diff --git a/dom/base/ChromeUtils.cpp b/dom/base/ChromeUtils.cpp
index 0c9542782e8c..d27780d4decd 100644
--- a/dom/base/ChromeUtils.cpp
+++ b/dom/base/ChromeUtils.cpp
@@ -26,7 +26,6 @@
 #include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/ContentParent.h"
 #include "mozilla/dom/IdleDeadline.h"
-#include "mozilla/dom/InProcessChild.h"
 #include "mozilla/dom/JSActorService.h"
 #include "mozilla/dom/MediaControlUtils.h"
 #include "mozilla/dom/MediaControlService.h"
@@ -1304,10 +1303,7 @@ void ChromeUtils::GenerateMediaControlKey(const GlobalObject& aGlobal,
 }
 
 /* static */
-nsIDOMProcessChild* ChromeUtils::GetDomProcessChild(const GlobalObject&) {
-  if (XRE_IsParentProcess()) {
-    return InProcessChild::Singleton();
-  }
+nsIContentChild* ChromeUtils::GetContentChild(const GlobalObject&) {
   return ContentChild::GetSingleton();
 }
 
diff --git a/dom/base/ChromeUtils.h b/dom/base/ChromeUtils.h
index 97092451ddb1..94a3044f5078 100644
--- a/dom/base/ChromeUtils.h
+++ b/dom/base/ChromeUtils.h
@@ -12,7 +12,7 @@
 #include "mozilla/dom/ChromeUtilsBinding.h"
 #include "mozilla/ErrorResult.h"
 #include "nsDOMNavigationTiming.h"  // for DOMHighResTimeStamp
-#include "nsIDOMProcessChild.h"
+#include "nsIContentChild.h"
 
 namespace mozilla {
 
@@ -218,7 +218,7 @@ class ChromeUtils {
   static void GenerateMediaControlKey(const GlobalObject& aGlobal,
                                       MediaControlKey aKey);
 
-  static nsIDOMProcessChild* GetDomProcessChild(const GlobalObject&);
+  static nsIContentChild* GetContentChild(const GlobalObject&);
 
   // This function would only be used for testing.
   static void GetCurrentActiveMediaMetadata(const GlobalObject& aGlobal,
diff --git a/dom/bindings/Bindings.conf b/dom/bindings/Bindings.conf
index 4e6e62c0b3d7..d858181b369d 100644
--- a/dom/bindings/Bindings.conf
+++ b/dom/bindings/Bindings.conf
@@ -1875,8 +1875,8 @@ addExternalIface('nsITreeSelection', nativeType='nsITreeSelection',
                  notflattened=True)
 addExternalIface('nsISupports', nativeType='nsISupports')
 addExternalIface('nsIDocShell', nativeType='nsIDocShell', notflattened=True)
-addExternalIface('nsIDOMProcessChild', nativeType='nsIDOMProcessChild', notflattened=True)
-addExternalIface('nsIDOMProcessParent', nativeType='nsIDOMProcessParent', notflattened=True)
+addExternalIface('nsIContentChild', nativeType='nsIContentChild', notflattened=True)
+addExternalIface('nsIContentParent', nativeType='nsIContentParent', notflattened=True)
 addExternalIface('nsIReferrerInfo', nativeType='nsIReferrerInfo', notflattened=True)
 addExternalIface('nsISecureBrowserUI', nativeType='nsISecureBrowserUI', notflattened=True)
 addExternalIface('nsIWebProgress', nativeType='nsIWebProgress', notflattened=True)
diff --git a/dom/chrome-webidl/ChromeUtils.webidl b/dom/chrome-webidl/ChromeUtils.webidl
index 1ff8ada3fd78..c0be3514627e 100644
--- a/dom/chrome-webidl/ChromeUtils.webidl
+++ b/dom/chrome-webidl/ChromeUtils.webidl
@@ -4,7 +4,7 @@
  * You can obtain one at http://mozilla.org/MPL/2.0/.
  */
 
-interface nsIDOMProcessChild;
+interface nsIContentChild;
 
 /**
  * An optimized QueryInterface method, generated by generateQI.
@@ -477,10 +477,10 @@ partial namespace ChromeUtils {
   void generateMediaControlKey(MediaControlKey aKey);
 
   /**
-   * nsIDOMProcessChild for the current process.
+   * ContentChild of the current process.
    */
   [ChromeOnly]
-  readonly attribute nsIDOMProcessChild? domProcessChild;
+  readonly attribute nsIContentChild? contentChild;
 
   // This is used to get the media metadata from the current main controller in
   // testing.
diff --git a/dom/chrome-webidl/JSProcessActor.webidl b/dom/chrome-webidl/JSProcessActor.webidl
index eea710b4d6fc..c70cd62208de 100644
--- a/dom/chrome-webidl/JSProcessActor.webidl
+++ b/dom/chrome-webidl/JSProcessActor.webidl
@@ -20,7 +20,7 @@ interface JSProcessActorParent {
   [ChromeOnly]
   constructor();
 
-  readonly attribute nsIDOMProcessParent manager;
+  readonly attribute nsIContentParent manager;
 };
 JSProcessActorParent includes JSActor;
 
@@ -29,7 +29,7 @@ interface JSProcessActorChild {
   [ChromeOnly]
   constructor();
 
-  readonly attribute nsIDOMProcessChild manager;
+  readonly attribute nsIContentChild manager;
 };
 JSProcessActorChild includes JSActor;
 
diff --git a/dom/chrome-webidl/WindowGlobalActors.webidl b/dom/chrome-webidl/WindowGlobalActors.webidl
index c754974a044f..85d2f36b5fbb 100644
--- a/dom/chrome-webidl/WindowGlobalActors.webidl
+++ b/dom/chrome-webidl/WindowGlobalActors.webidl
@@ -8,7 +8,7 @@ interface URI;
 interface nsIDocShell;
 interface RemoteTab;
 interface nsITransportSecurityInfo;
-interface nsIDOMProcessParent;
+interface nsIContentParent;
 
 [Exposed=Window, ChromeOnly]
 interface WindowContext {
@@ -62,10 +62,9 @@ interface WindowGlobalParent : WindowContext {
   // String containing serialized content blocking log.
   readonly attribute DOMString contentBlockingLog;
 
-  // DOM Process which this window was loaded in. Will be either InProcessParent
-  // for windows loaded in the parent process, or ContentParent for windows
-  // loaded in the content process.
-  readonly attribute nsIDOMProcessParent? domProcess;
+  // ContentParent of the process this window is loaded in.
+  // Will be `null` for windows loaded in the parent process.
+  readonly attribute nsIContentParent? contentParent;
 
   static WindowGlobalParent? getByInnerWindowId(unsigned long long innerWindowId);
 
diff --git a/dom/docs/Fission.rst b/dom/docs/Fission.rst
index 532c69332cb5..673d0ee31167 100644
--- a/dom/docs/Fission.rst
+++ b/dom/docs/Fission.rst
@@ -583,11 +583,11 @@ Get a JSProcessActor
   let parentActor = this.browser
     .browsingContext
     .currentWindowGlobal
-    .domProcess
+    .contentParent
     .getActor("TestProcess");
 
   // get child side actor
-  let childActor = ChromeUtils.domProcessChild
+  let childActor = ChromeUtils.contentChild
     .getActor("TestProcess");
 
 And more
diff --git a/dom/ipc/ContentChild.cpp b/dom/ipc/ContentChild.cpp
index a3846b8189fa..ae85a9db8084 100644
--- a/dom/ipc/ContentChild.cpp
+++ b/dom/ipc/ContentChild.cpp
@@ -50,7 +50,6 @@
 #include "mozilla/dom/DocGroup.h"
 #include "mozilla/dom/ExternalHelperAppChild.h"
 #include "mozilla/dom/GetFilesHelper.h"
-#include "mozilla/dom/InProcessChild.h"
 #include "mozilla/dom/IPCBlobInputStreamChild.h"
 #include "mozilla/dom/IPCBlobUtils.h"
 #include "mozilla/dom/JSActorService.h"
@@ -79,6 +78,7 @@
 #include "mozilla/ipc/FileDescriptorSetChild.h"
 #include "mozilla/ipc/FileDescriptorUtils.h"
 #include "mozilla/ipc/GeckoChildProcessHost.h"
+#include "mozilla/ipc/InProcessChild.h"
 #include "mozilla/ipc/LibrarySandboxPreload.h"
 #include "mozilla/ipc/ProcessChild.h"
 #include "mozilla/ipc/PChildToParentStreamChild.h"
@@ -612,8 +612,8 @@ ContentChild::~ContentChild() {
 #endif
 
 NS_INTERFACE_MAP_BEGIN(ContentChild)
-  NS_INTERFACE_MAP_ENTRY(nsIDOMProcessChild)
-  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIDOMProcessChild)
+  NS_INTERFACE_MAP_ENTRY(nsIContentChild)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIContentChild)
 NS_INTERFACE_MAP_END
 
 mozilla::ipc::IPCResult ContentChild::RecvSetXPCOMProcessAttributes(
@@ -4195,24 +4195,58 @@ NS_IMETHODIMP ContentChild::GetActor(const nsACString& aName,
 IPCResult ContentChild::RecvRawMessage(const JSActorMessageMeta& aMeta,
                                        const ClonedMessageData& aData,
                                        const ClonedMessageData& aStack) {
-  RefPtr<JSProcessActorChild> actor;
-  GetActor(aMeta.actorName(), getter_AddRefs(actor));
-  if (actor) {
-    StructuredCloneData data;
-    data.BorrowFromClonedMessageDataForChild(aData);
-    StructuredCloneData stack;
-    stack.BorrowFromClonedMessageDataForChild(aStack);
-    actor->ReceiveRawMessage(aMeta, std::move(data), std::move(stack));
-  }
+  StructuredCloneData data;
+  data.BorrowFromClonedMessageDataForChild(aData);
+  StructuredCloneData stack;
+  stack.BorrowFromClonedMessageDataForChild(aStack);
+  ReceiveRawMessage(aMeta, std::move(data), std::move(stack));
   return IPC_OK();
 }
 
-NS_IMETHODIMP ContentChild::GetCanSend(bool* aCanSend) {
-  *aCanSend = CanSend();
-  return NS_OK;
+void ContentChild::ReceiveRawMessage(const JSActorMessageMeta& aMeta,
+                                     StructuredCloneData&& aData,
+                                     StructuredCloneData&& aStack) {
+  RefPtr<JSProcessActorChild> actor =
+      GetActor(aMeta.actorName(), IgnoreErrors());
+  if (actor) {
+    actor->ReceiveRawMessage(aMeta, std::move(aData), std::move(aStack));
+  }
 }
 
-NS_IMETHODIMP_(ContentChild*) ContentChild::AsContentChild() { return this; }
+already_AddRefed<mozilla::dom::JSProcessActorChild> ContentChild::GetActor(
+    const nsACString& aName, ErrorResult& aRv) {
+  if (!CanSend()) {
+    aRv.ThrowInvalidStateError(
+        "Cannot get JSProcessActor, process is shutting down");
+    return nullptr;
+  }
+
+  // Check if this actor has already been created, and return it if it has.
+  if (mProcessActors.Contains(aName)) {
+    return mProcessActors.Get(aName);
+  }
+
+  // Otherwise, we want to create a new instance of this actor.
+  JS::RootedObject obj(RootingCx());
+  ConstructActor(aName, &obj, aRv);
+  if (aRv.Failed()) {
+    return nullptr;
+  }
+
+  // Unwrap our actor to a JSProcessActorChild object.
+  RefPtr<JSProcessActorChild> actor;
+  if (NS_FAILED(UNWRAP_OBJECT(JSProcessActorChild, &obj, actor))) {
+    aRv.ThrowTypeMismatchError(
+        "Constructed actor does not inherit from JSProcessActorChild");
+    return nullptr;
+  }
+
+  MOZ_RELEASE_ASSERT(!actor->Manager(),
+                     "mManager was already initialized once!");
+  actor->Init(aName, this);
+  mProcessActors.Put(aName, RefPtr{actor});
+  return actor.forget();
+}
 
 IPCResult ContentChild::RecvFlushFOGData(FlushFOGDataResolver&& aResolver) {
 #ifdef MOZ_GLEAN
diff --git a/dom/ipc/ContentChild.h b/dom/ipc/ContentChild.h
index 863318ac5679..7d7d4f6e93eb 100644
--- a/dom/ipc/ContentChild.h
+++ b/dom/ipc/ContentChild.h
@@ -21,7 +21,7 @@
 #include "mozilla/ipc/InputStreamUtils.h"
 #include "mozilla/ipc/Shmem.h"
 #include "nsHashKeys.h"
-#include "nsIDOMProcessChild.h"
+#include "nsIContentChild.h"
 #include "nsIObserver.h"
 #include "nsTHashtable.h"
 #include "nsStringFwd.h"
@@ -42,6 +42,7 @@ struct LookAndFeelInt;
 class nsDocShellLoadState;
 class nsFrameLoader;
 class nsIOpenWindowInfo;
+class JSProcessActorChild;
 
 namespace mozilla {
 class RemoteSpellcheckEngineChild;
@@ -73,7 +74,7 @@ class GetFilesHelperChild;
 class TabContext;
 
 class ContentChild final : public PContentChild,
-                           public nsIDOMProcessChild,
+                           public nsIContentChild,
                            public mozilla::ipc::IShmemAllocator,
                            public mozilla::ipc::ChildToParentStreamActorManager,
                            public ProcessActor {
@@ -84,7 +85,7 @@ class ContentChild final : public PContentChild,
   friend class PContentChild;
 
  public:
-  NS_DECL_NSIDOMPROCESSCHILD
+  NS_DECL_NSICONTENTCHILD
 
   ContentChild();
   virtual ~ContentChild();
@@ -678,6 +679,10 @@ class ContentChild final : public PContentChild,
   PFileDescriptorSetChild* SendPFileDescriptorSetConstructor(
       const FileDescriptor& aFD) override;
 
+  // Get a JS actor object by name.
+  already_AddRefed<mozilla::dom::JSProcessActorChild> GetActor(
+      const nsACString& aName, ErrorResult& aRv);
+
  private:
   static void ForceKillTimerCallback(nsITimer* aTimer, void* aClosure);
   void StartForceKillTimer();
@@ -777,6 +782,10 @@ class ContentChild final : public PContentChild,
                                          const ClonedMessageData& aData,
                                          const ClonedMessageData& aStack);
 
+  void ReceiveRawMessage(const JSActorMessageMeta& aMeta,
+                         ipc::StructuredCloneData&& aData,
+                         ipc::StructuredCloneData&& aStack);
+
   JSActor::Type GetSide() override { return JSActor::Type::Child; }
 
   mozilla::ipc::IPCResult RecvHistoryCommitLength(
@@ -883,7 +892,7 @@ class ContentChild final : public PContentChild,
 };
 
 inline nsISupports* ToSupports(mozilla::dom::ContentChild* aContentChild) {
-  return static_cast<nsIDOMProcessChild*>(aContentChild);
+  return static_cast<nsIContentChild*>(aContentChild);
 }
 
 }  // namespace dom
diff --git a/dom/ipc/ContentParent.cpp b/dom/ipc/ContentParent.cpp
index 8090b15b9d2e..1b6b35c12ce6 100644
--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -3184,13 +3184,13 @@ NS_IMPL_CYCLE_COLLECTING_RELEASE(ContentParent)
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ContentParent)
   NS_INTERFACE_MAP_ENTRY_CONCRETE(ContentParent)
-  NS_INTERFACE_MAP_ENTRY(nsIDOMProcessParent)
+  NS_INTERFACE_MAP_ENTRY(nsIContentParent)
   NS_INTERFACE_MAP_ENTRY(nsIObserver)
   NS_INTERFACE_MAP_ENTRY(nsIDOMGeoPositionCallback)
   NS_INTERFACE_MAP_ENTRY(nsIDOMGeoPositionErrorCallback)
   NS_INTERFACE_MAP_ENTRY(nsIAsyncShutdownBlocker)
   NS_INTERFACE_MAP_ENTRY(nsIInterfaceRequestor)
-  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIDOMProcessParent)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIContentParent)
 NS_INTERFACE_MAP_END
 
 // Async shutdown blocker
@@ -6819,18 +6819,60 @@ NS_IMETHODIMP ContentParent::GetChildID(uint64_t* aOut) {
 IPCResult ContentParent::RecvRawMessage(const JSActorMessageMeta& aMeta,
                                         const ClonedMessageData& aData,
                                         const ClonedMessageData& aStack) {
-  RefPtr<JSProcessActorParent> actor;
-  GetActor(aMeta.actorName(), getter_AddRefs(actor));
-  if (actor) {
-    StructuredCloneData data;
-    data.BorrowFromClonedMessageDataForParent(aData);
-    StructuredCloneData stack;
-    stack.BorrowFromClonedMessageDataForParent(aStack);
-    actor->ReceiveRawMessage(aMeta, std::move(data), std::move(stack));
-  }
+  StructuredCloneData data;
+  data.BorrowFromClonedMessageDataForParent(aData);
+  StructuredCloneData stack;
+  stack.BorrowFromClonedMessageDataForParent(aStack);
+  ReceiveRawMessage(aMeta, std::move(data), std::move(stack));
   return IPC_OK();
 }
 
+void ContentParent::ReceiveRawMessage(const JSActorMessageMeta& aMeta,
+                                      StructuredCloneData&& aData,
+                                      StructuredCloneData&& aStack) {
+  RefPtr<JSProcessActorParent> actor =
+      GetActor(aMeta.actorName(), IgnoreErrors());
+  if (actor) {
+    actor->ReceiveRawMessage(aMeta, std::move(aData), std::move(aStack));
+  }
+}
+
+already_AddRefed<JSProcessActorParent> ContentParent::GetActor(
+    const nsACString& aName, ErrorResult& aRv) {
+  if (!CanSend()) {
+    aRv.ThrowInvalidStateError(nsPrintfCString(
+        "Cannot get actor '%s': content parent is ready to communicate.",
+        PromiseFlatCString(aName).get()));
+    return nullptr;
+  }
+
+  // Check if this actor has already been created, and return it if it has.
+  if (mProcessActors.Contains(aName)) {
+    return do_AddRef(mProcessActors.GetWeak(aName));
+  }
+
+  // Otherwise, we want to create a new instance of this actor.
+  JS::RootedObject obj(RootingCx());
+  ConstructActor(aName, &obj, aRv);
+  if (aRv.Failed()) {
+    return nullptr;
+  }
+
+  // Unwrap our actor to a JSProcessActorParent object.
+  RefPtr<JSProcessActorParent> actor;
+  if (NS_FAILED(UNWRAP_OBJECT(JSProcessActorParent, &obj, actor))) {
+    aRv.ThrowTypeMismatchError(
+        "Constructed actor does not inherit from JSProcessActorParent");
+    return nullptr;
+  }
+
+  MOZ_RELEASE_ASSERT(!actor->Manager(),
+                     "mManager was already initialized once!");
+  actor->Init(aName, this);
+  mProcessActors.Put(aName, RefPtr{actor});
+  return actor.forget();
+}
+
 NS_IMETHODIMP ContentParent::GetActor(const nsACString& aName,
                                       JSProcessActorParent** retval) {
   if (!CanSend()) {
@@ -6874,13 +6916,6 @@ IPCResult ContentParent::RecvFOGData(ByteBuf&& buf) {
   return IPC_OK();
 }
 
-NS_IMETHODIMP ContentParent::GetCanSend(bool* aCanSend) {
-  *aCanSend = CanSend();
-  return NS_OK;
-}
-
-NS_IMETHODIMP_(ContentParent*) ContentParent::AsContentParent() { return this; }
-
 }  // namespace dom
 }  // namespace mozilla
 
diff --git a/dom/ipc/ContentParent.h b/dom/ipc/ContentParent.h
index 51710457a61c..274e8ebac66a 100644
--- a/dom/ipc/ContentParent.h
+++ b/dom/ipc/ContentParent.h
@@ -36,7 +36,7 @@
 #include "nsFrameMessageManager.h"
 #include "nsHashKeys.h"
 #include "nsIAsyncShutdown.h"
-#include "nsIDOMProcessParent.h"
+#include "nsIContentParent.h"
 #include "nsIInterfaceRequestor.h"
 #include "nsIObserver.h"
 #include "nsIRemoteTab.h"
@@ -128,7 +128,7 @@ struct CancelContentJSOptions;
 
 class ContentParent final
     : public PContentParent,
-      public nsIDOMProcessParent,
+      public nsIContentParent,
       public nsIObserver,
       public nsIDOMGeoPositionCallback,
       public nsIDOMGeoPositionErrorCallback,
@@ -357,7 +357,7 @@ class ContentParent final
   NS_DECL_CYCLE_COLLECTION_CLASS_AMBIGUOUS(ContentParent, nsIObserver)
 
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS
-  NS_DECL_NSIDOMPROCESSPARENT
+  NS_DECL_NSICONTENTPARENT
   NS_DECL_NSIOBSERVER
   NS_DECL_NSIDOMGEOPOSITIONCALLBACK
   NS_DECL_NSIDOMGEOPOSITIONERRORCALLBACK
@@ -1358,6 +1358,13 @@ class ContentParent final
       nsTArray<ContentParent*>& aContentParents, uint32_t aMaxContentParents,
       bool aPreferUsed);
 
+  // Get a JS actor object by name.
+  already_AddRefed<JSProcessActorParent> GetActor(const nsACString& aName,
+                                                  ErrorResult& aRv);
+  void ReceiveRawMessage(const JSActorMessageMeta& aMeta,
+                         StructuredCloneData&& aData,
+                         StructuredCloneData&& aStack);
+
   void AddToPool(nsTArray<ContentParent*>&);
   void RemoveFromPool(nsTArray<ContentParent*>&);
   void AssertNotInPool();
@@ -1540,7 +1547,7 @@ bool IsWebRemoteType(const nsAString& aContentProcessType);
 bool IsWebCoopCoepRemoteType(const nsAString& aContentProcessType);
 
 inline nsISupports* ToSupports(mozilla::dom::ContentParent* aContentParent) {
-  return static_cast<nsIDOMProcessParent*>(aContentParent);
+  return static_cast<nsIContentParent*>(aContentParent);
 }
 
 }  // namespace dom
diff --git a/dom/ipc/JSProcessActorChild.cpp b/dom/ipc/JSProcessActorChild.cpp
index 7d6aa85b9503..3b4f28f3725d 100644
--- a/dom/ipc/JSProcessActorChild.cpp
+++ b/dom/ipc/JSProcessActorChild.cpp
@@ -6,7 +6,7 @@
 
 #include "mozilla/dom/JSProcessActorBinding.h"
 #include "mozilla/dom/JSProcessActorChild.h"
-#include "mozilla/dom/InProcessChild.h"
+#include "mozilla/ipc/InProcessChild.h"
 
 namespace mozilla {
 namespace dom {
@@ -27,44 +27,14 @@ JSObject* JSProcessActorChild::WrapObject(JSContext* aCx,
   return JSProcessActorChild_Binding::Wrap(aCx, this, aGivenProto);
 }
 
-namespace {
-
-class AsyncMessageToProcessParent : public Runnable {
- public:
-  AsyncMessageToProcessParent(const JSActorMessageMeta& aMetadata,
-                              ipc::StructuredCloneData&& aData,
-                              ipc::StructuredCloneData&& aStack)
-      : mozilla::Runnable("InProcessParent::HandleAsyncMessage"),
-        mMetadata(aMetadata),
-        mData(std::move(aData)),
-        mStack(std::move(aStack)) {}
-
-  NS_IMETHOD Run() override {
-    MOZ_ASSERT(NS_IsMainThread(), "Should be called on the main thread.");
-    if (auto* parent = InProcessParent::Singleton()) {
-      RefPtr<JSProcessActorParent> actor;
-      parent->GetActor(mMetadata.actorName(), getter_AddRefs(actor));
-      if (actor) {
-        actor->ReceiveRawMessage(mMetadata, std::move(mData),
-                                 std::move(mStack));
-      }
-    }
-    return NS_OK;
-  }
-
- private:
-  JSActorMessageMeta mMetadata;
-  ipc::StructuredCloneData mData;
-  ipc::StructuredCloneData mStack;
-};
-
-}  // namespace
-
 void JSProcessActorChild::SendRawMessage(const JSActorMessageMeta& aMeta,
                                          ipc::StructuredCloneData&& aData,
                                          ipc::StructuredCloneData&& aStack,
                                          ErrorResult& aRv) {
-  if (NS_WARN_IF(!mCanSend || !mManager || !mManager->GetCanSend())) {
+  // We only ever have JSProcessActorChild in a multi-process scenario.
+  MOZ_ASSERT(XRE_IsContentProcess());
+
+  if (NS_WARN_IF(!mCanSend || !mManager || !mManager->CanSend())) {
     aRv.ThrowInvalidStateError("JSProcessActorChild cannot send at the moment");
     return;
   }
@@ -78,29 +48,17 @@ void JSProcessActorChild::SendRawMessage(const JSActorMessageMeta& aMeta,
     return;
   }
 
-  // If the parent side is in the same process, we have a PInProcess manager,
-  // and can dispatch the message directly to the event loop.
-  ContentChild* contentChild = mManager->AsContentChild();
-  if (!contentChild) {
-    MOZ_DIAGNOSTIC_ASSERT(XRE_IsParentProcess());
-    NS_DispatchToMainThread(MakeAndAddRef<AsyncMessageToProcessParent>(
-        aMeta, std::move(aData), std::move(aStack)));
-    return;
-  }
-
   ClonedMessageData msgData;
   ClonedMessageData stackData;
-  if (NS_WARN_IF(
-          !aData.BuildClonedMessageDataForChild(contentChild, msgData)) ||
-      NS_WARN_IF(
-          !aStack.BuildClonedMessageDataForChild(contentChild, stackData))) {
+  if (NS_WARN_IF(!aData.BuildClonedMessageDataForChild(mManager, msgData)) ||
+      NS_WARN_IF(!aStack.BuildClonedMessageDataForChild(mManager, stackData))) {
     aRv.ThrowDataCloneError(nsPrintfCString(
         "JSProcessActorChild serialization error: cannot clone, in actor '%s'",
         PromiseFlatCString(aMeta.actorName()).get()));
     return;
   }
 
-  if (NS_WARN_IF(!contentChild->SendRawMessage(aMeta, msgData, stackData))) {
+  if (NS_WARN_IF(!mManager->SendRawMessage(aMeta, msgData, stackData))) {
     aRv.ThrowOperationError(
         nsPrintfCString("JSProcessActorChild send error in actor '%s'",
                         PromiseFlatCString(aMeta.actorName()).get()));
@@ -109,7 +67,7 @@ void JSProcessActorChild::SendRawMessage(const JSActorMessageMeta& aMeta,
 }
 
 void JSProcessActorChild::Init(const nsACString& aName,
-                               nsIDOMProcessChild* aManager) {
+                               ContentChild* aManager) {
   MOZ_ASSERT(!mManager, "Cannot Init() a JSProcessActorChild twice!");
   SetName(aName);
   mManager = aManager;
diff --git a/dom/ipc/JSProcessActorChild.h b/dom/ipc/JSProcessActorChild.h
index 186930d294b5..ec74ec233ead 100644
--- a/dom/ipc/JSProcessActorChild.h
+++ b/dom/ipc/JSProcessActorChild.h
@@ -7,8 +7,8 @@
 #ifndef mozilla_dom_JSProcessActorChild_h
 #define mozilla_dom_JSProcessActorChild_h
 
+#include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/JSActor.h"
-#include "nsIDOMProcessChild.h"
 
 namespace mozilla {
 namespace dom {
@@ -32,9 +32,9 @@ class JSProcessActorChild final : public JSActor {
     return MakeAndAddRef<JSProcessActorChild>();
   }
 
-  nsIDOMProcessChild* Manager() const { return mManager; }
+  ContentChild* Manager() const { return mManager; }
 
-  void Init(const nsACString& aName, nsIDOMProcessChild* aManager);
+  void Init(const nsACString& aName, ContentChild* aManager);
   void AfterDestroy();
 
  protected:
@@ -50,7 +50,7 @@ class JSProcessActorChild final : public JSActor {
   ~JSProcessActorChild() { MOZ_ASSERT(!mManager); }
 
   bool mCanSend = true;
-  nsCOMPtr<nsIDOMProcessChild> mManager;
+  RefPtr<ContentChild> mManager;
 };
 
 }  // namespace dom
diff --git a/dom/ipc/JSProcessActorParent.cpp b/dom/ipc/JSProcessActorParent.cpp
index 1e9634135689..17528b250629 100644
--- a/dom/ipc/JSProcessActorParent.cpp
+++ b/dom/ipc/JSProcessActorParent.cpp
@@ -27,7 +27,7 @@ JSObject* JSProcessActorParent::WrapObject(JSContext* aCx,
 }
 
 void JSProcessActorParent::Init(const nsACString& aName,
-                                nsIDOMProcessParent* aManager) {
+                                ContentParent* aManager) {
   MOZ_ASSERT(!mManager, "Cannot Init() a JSProcessActorParent twice!");
   SetName(aName);
   mManager = aManager;
@@ -37,44 +37,11 @@ void JSProcessActorParent::Init(const nsACString& aName,
 
 JSProcessActorParent::~JSProcessActorParent() { MOZ_ASSERT(!mManager); }
 
-namespace {
-
-class AsyncMessageToProcessChild : public Runnable {
- public:
-  AsyncMessageToProcessChild(const JSActorMessageMeta& aMetadata,
-                             ipc::StructuredCloneData&& aData,
-                             ipc::StructuredCloneData&& aStack)
-      : mozilla::Runnable("InProcessChild::HandleAsyncMessage"),
-        mMetadata(aMetadata),
-        mData(std::move(aData)),
-        mStack(std::move(aStack)) {}
-
-  NS_IMETHOD Run() override {
-    MOZ_ASSERT(NS_IsMainThread(), "Should be called on the main thread.");
-    if (auto* child = InProcessChild::Singleton()) {
-      RefPtr<JSProcessActorChild> actor;
-      child->GetActor(mMetadata.actorName(), getter_AddRefs(actor));
-      if (actor) {
-        actor->ReceiveRawMessage(mMetadata, std::move(mData),
-                                 std::move(mStack));
-      }
-    }
-    return NS_OK;
-  }
-
- private:
-  JSActorMessageMeta mMetadata;
-  ipc::StructuredCloneData mData;
-  ipc::StructuredCloneData mStack;
-};
-
-}  // namespace
-
 void JSProcessActorParent::SendRawMessage(const JSActorMessageMeta& aMeta,
                                           ipc::StructuredCloneData&& aData,
                                           ipc::StructuredCloneData&& aStack,
                                           ErrorResult& aRv) {
-  if (NS_WARN_IF(!mCanSend || !mManager || !mManager->GetCanSend())) {
+  if (NS_WARN_IF(!mCanSend || !mManager || !mManager->CanSend())) {
     aRv.ThrowInvalidStateError(
         nsPrintfCString("Actor '%s' cannot send message '%s' during shutdown.",
                         PromiseFlatCString(aMeta.actorName()).get(),
@@ -91,22 +58,12 @@ void JSProcessActorParent::SendRawMessage(const JSActorMessageMeta& aMeta,
     return;
   }
 
-  // If the parent side is in the same process, we have a PInProcess manager,
-  // and can dispatch the message directly to the event loop.
-  ContentParent* contentParent = mManager->AsContentParent();
-  if (!contentParent) {
-    NS_DispatchToMainThread(MakeAndAddRef<AsyncMessageToProcessChild>(
-        aMeta, std::move(aData), std::move(aStack)));
-    return;
-  }
-
   // Cross-process case - send data over ContentParent to other side.
   ClonedMessageData msgData;
   ClonedMessageData stackData;
-  if (NS_WARN_IF(
-          !aData.BuildClonedMessageDataForParent(contentParent, msgData)) ||
+  if (NS_WARN_IF(!aData.BuildClonedMessageDataForParent(mManager, msgData)) ||
       NS_WARN_IF(
-          !aStack.BuildClonedMessageDataForParent(contentParent, stackData))) {
+          !aStack.BuildClonedMessageDataForParent(mManager, stackData))) {
     aRv.ThrowDataCloneError(
         nsPrintfCString("Actor '%s' cannot send message '%s': cannot clone.",
                         PromiseFlatCString(aMeta.actorName()).get(),
@@ -114,7 +71,7 @@ void JSProcessActorParent::SendRawMessage(const JSActorMessageMeta& aMeta,
     return;
   }
 
-  if (NS_WARN_IF(!contentParent->SendRawMessage(aMeta, msgData, stackData))) {
+  if (NS_WARN_IF(!mManager->SendRawMessage(aMeta, msgData, stackData))) {
     aRv.Throw(NS_ERROR_UNEXPECTED);
     return;
   }
diff --git a/dom/ipc/JSProcessActorParent.h b/dom/ipc/JSProcessActorParent.h
index cfcdc0343a14..33a01dd6ef9f 100644
--- a/dom/ipc/JSProcessActorParent.h
+++ b/dom/ipc/JSProcessActorParent.h
@@ -15,7 +15,6 @@
 #include "mozilla/dom/JSActor.h"
 #include "mozilla/extensions/WebExtensionContentScript.h"
 #include "nsCycleCollectionParticipant.h"
-#include "nsIDOMProcessParent.h"
 #include "nsWrapperCache.h"
 
 namespace mozilla {
@@ -39,9 +38,9 @@ class JSProcessActorParent final : public JSActor {
     return MakeAndAddRef<JSProcessActorParent>();
   }
 
-  nsIDOMProcessParent* Manager() const { return mManager; }
+  ContentParent* Manager() const { return mManager; }
 
-  void Init(const nsACString& aName, nsIDOMProcessParent* aManager);
+  void Init(const nsACString& aName, ContentParent* aManager);
   void AfterDestroy();
 
  protected:
@@ -57,7 +56,7 @@ class JSProcessActorParent final : public JSActor {
   ~JSProcessActorParent();
 
   bool mCanSend = true;
-  nsCOMPtr<nsIDOMProcessParent> mManager;
+  RefPtr<ContentParent> mManager;
 };
 
 }  // namespace dom
diff --git a/dom/ipc/JSProcessActorProtocol.cpp b/dom/ipc/JSProcessActorProtocol.cpp
index a90dd054c459..cae0e0d0f509 100644
--- a/dom/ipc/JSProcessActorProtocol.cpp
+++ b/dom/ipc/JSProcessActorProtocol.cpp
@@ -78,18 +78,16 @@ NS_IMETHODIMP JSProcessActorProtocol::Observe(nsISupports* aSubject,
                                               const char* aTopic,
                                               const char16_t* aData) {
   MOZ_ASSERT(nsContentUtils::IsSafeToRunScript());
+  MOZ_ASSERT(!XRE_IsParentProcess());
 
-  nsCOMPtr<nsIDOMProcessChild> manager;
-  if (XRE_IsParentProcess()) {
-    manager = InProcessChild::Singleton();
-  } else {
-    manager = ContentChild::GetSingleton();
-  }
+  ErrorResult error;
+  RefPtr<JSProcessActorChild> actor =
+      ContentChild::GetSingleton()->GetActor(mName, error);
+
+  // Don't raise an error if creation of our actor was vetoed.
+  if (NS_WARN_IF(error.Failed())) {
+    nsresult rv = error.StealNSResult();
 
-  RefPtr<JSProcessActorChild> actor;
-  nsresult rv = manager->GetActor(mName, getter_AddRefs(actor));
-  if (NS_WARN_IF(NS_FAILED(rv))) {
-    // Don't raise an error if creation of our actor was vetoed.
     if (rv == NS_ERROR_NOT_AVAILABLE) {
       return NS_OK;
     }
@@ -107,6 +105,12 @@ NS_IMETHODIMP JSProcessActorProtocol::Observe(nsISupports* aSubject,
 }
 
 void JSProcessActorProtocol::AddObservers() {
+  // Ignore adding observers for parent processes, but this will
+  // need to change with bug 1633379.
+  if (XRE_IsParentProcess()) {
+    return;
+  }
+
   nsCOMPtr<nsIObserverService> os = services::GetObserverService();
   for (auto& topic : mChild.mObservers) {
     // This makes the observer service hold an owning reference to the
diff --git a/dom/ipc/JSWindowActorChild.h b/dom/ipc/JSWindowActorChild.h
index 289fd61bb40b..bed53415ad67 100644
--- a/dom/ipc/JSWindowActorChild.h
+++ b/dom/ipc/JSWindowActorChild.h
@@ -15,7 +15,7 @@
 #include "mozilla/dom/JSActor.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
-#include "nsIDOMProcessChild.h"
+#include "nsIContentChild.h"
 
 namespace mozilla {
 namespace dom {
diff --git a/dom/ipc/PropertyBagUtils.cpp b/dom/ipc/PropertyBagUtils.cpp
index eaed6beb5978..bf224d92ad90 100644
--- a/dom/ipc/PropertyBagUtils.cpp
+++ b/dom/ipc/PropertyBagUtils.cpp
@@ -16,7 +16,6 @@
 #include "nsVariant.h"
 
 using namespace IPC;
-using namespace mozilla::dom;
 
 namespace mozilla {
 namespace ipc {
diff --git a/dom/ipc/WindowGlobalChild.cpp b/dom/ipc/WindowGlobalChild.cpp
index 1bd23184c3e3..3c438b0db3ee 100644
--- a/dom/ipc/WindowGlobalChild.cpp
+++ b/dom/ipc/WindowGlobalChild.cpp
@@ -20,8 +20,8 @@
 #include "mozilla/dom/WindowGlobalActorsBinding.h"
 #include "mozilla/dom/WindowGlobalParent.h"
 #include "mozilla/dom/WindowContext.h"
-#include "mozilla/dom/InProcessChild.h"
-#include "mozilla/dom/InProcessParent.h"
+#include "mozilla/ipc/InProcessChild.h"
+#include "mozilla/ipc/InProcessParent.h"
 #include "nsContentUtils.h"
 #include "nsDocShell.h"
 #include "nsFocusManager.h"
diff --git a/dom/ipc/WindowGlobalParent.cpp b/dom/ipc/WindowGlobalParent.cpp
index 4da750763e39..d04822874fcd 100644
--- a/dom/ipc/WindowGlobalParent.cpp
+++ b/dom/ipc/WindowGlobalParent.cpp
@@ -10,7 +10,7 @@
 
 #include "mozilla/AsyncEventDispatcher.h"
 #include "mozilla/ClearOnShutdown.h"
-#include "mozilla/dom/InProcessParent.h"
+#include "mozilla/ipc/InProcessParent.h"
 #include "mozilla/dom/BrowserBridgeParent.h"
 #include "mozilla/dom/CanonicalBrowsingContext.h"
 #include "mozilla/dom/ClientInfo.h"
@@ -213,13 +213,6 @@ already_AddRefed<BrowserParent> WindowGlobalParent::GetBrowserParent() {
   return do_AddRef(static_cast<BrowserParent*>(Manager()));
 }
 
-ContentParent* WindowGlobalParent::GetContentParent() {
-  if (IsInProcess() || !CanSend()) {
-    return nullptr;
-  }
-  return static_cast<ContentParent*>(Manager()->Manager());
-}
-
 already_AddRefed<nsFrameLoader> WindowGlobalParent::GetRootFrameLoader() {
   dom::BrowsingContext* top = BrowsingContext()->Top();
 
@@ -830,11 +823,13 @@ nsIGlobalObject* WindowGlobalParent::GetParentObject() {
   return xpc::NativeGlobal(xpc::PrivilegedJunkScope());
 }
 
-nsIDOMProcessParent* WindowGlobalParent::GetDomProcess() {
-  if (RefPtr<BrowserParent> browserParent = GetBrowserParent()) {
-    return browserParent->Manager();
+nsIContentParent* WindowGlobalParent::GetContentParent() {
+  RefPtr<BrowserParent> browserParent = GetBrowserParent();
+  if (!browserParent) {
+    return nullptr;
   }
-  return InProcessParent::Singleton();
+
+  return browserParent->Manager();
 }
 
 void WindowGlobalParent::DidBecomeCurrentWindowGlobal(bool aCurrent) {
diff --git a/dom/ipc/WindowGlobalParent.h b/dom/ipc/WindowGlobalParent.h
index 12c2d92d4e7f..380d5df21288 100644
--- a/dom/ipc/WindowGlobalParent.h
+++ b/dom/ipc/WindowGlobalParent.h
@@ -20,7 +20,7 @@
 #include "nsRefPtrHashtable.h"
 #include "nsWrapperCache.h"
 #include "nsISupports.h"
-#include "nsIDOMProcessParent.h"
+#include "nsIContentParent.h"
 #include "mozilla/dom/WindowGlobalActor.h"
 #include "mozilla/dom/CanonicalBrowsingContext.h"
 #include "mozilla/net/CookieJarSettings.h"
@@ -93,8 +93,6 @@ class WindowGlobalParent final : public WindowContext,
   // |nullptr| if the actor has been torn down, or is in-process.
   already_AddRefed<BrowserParent> GetBrowserParent();
 
-  ContentParent* GetContentParent();
-
   void ReceiveRawMessage(const JSActorMessageMeta& aMeta,
                          ipc::StructuredCloneData&& aData,
                          ipc::StructuredCloneData&& aStack);
@@ -175,7 +173,7 @@ class WindowGlobalParent final : public WindowContext,
 
   ContentBlockingLog* GetContentBlockingLog() { return &mContentBlockingLog; }
 
-  nsIDOMProcessParent* GetDomProcess();
+  nsIContentParent* GetContentParent();
 
   nsICookieJarSettings* CookieJarSettings() { return mCookieJarSettings; }
 
diff --git a/dom/ipc/moz.build b/dom/ipc/moz.build
index 4395c178532e..9f36416b14da 100644
--- a/dom/ipc/moz.build
+++ b/dom/ipc/moz.build
@@ -8,8 +8,8 @@ with Files("**"):
     BUG_COMPONENT = ("Core", "DOM: Content Processes")
 
 XPIDL_SOURCES += [
-    'nsIDOMProcessChild.idl',
-    'nsIDOMProcessParent.idl',
+    'nsIContentChild.idl',
+    'nsIContentParent.idl',
     'nsIHangReport.idl',
 ]
 
@@ -48,8 +48,6 @@ EXPORTS.mozilla.dom += [
     'DocShellMessageUtils.h',
     'EffectsInfo.h',
     'FilePickerParent.h',
-    'InProcessChild.h',
-    'InProcessParent.h',
     'JSActor.h',
     'JSActorService.h',
     'JSProcessActorChild.h',
@@ -107,7 +105,6 @@ UNIFIED_SOURCES += [
     'CSPMessageUtils.cpp',
     'DocShellMessageUtils.cpp',
     'FilePickerParent.cpp',
-    'InProcessImpl.cpp',
     'JSActor.cpp',
     'JSActorService.cpp',
     'JSProcessActorChild.cpp',
@@ -161,7 +158,6 @@ IPDL_SOURCES += [
     'PContentPermissionRequest.ipdl',
     'PCycleCollectWithLogs.ipdl',
     'PFilePicker.ipdl',
-    'PInProcess.ipdl',
     'PLoginReputation.ipdl',
     'PPluginWidget.ipdl',
     'PProcessHangMonitor.ipdl',
diff --git a/dom/ipc/nsIContentChild.idl b/dom/ipc/nsIContentChild.idl
new file mode 100644
index 000000000000..82a1bbc9990d
--- /dev/null
+++ b/dom/ipc/nsIContentChild.idl
@@ -0,0 +1,11 @@
+#include "nsISupports.idl"
+
+webidl JSProcessActorChild;
+
+[scriptable, builtinclass, uuid(b0c6e5f3-02f1-4f11-a0af-336fc231f3bf)]
+interface nsIContentChild: nsISupports {
+    // Internal ID of the process.
+    readonly attribute unsigned long long childID;
+
+    JSProcessActorChild getActor(in ACString name);
+};
diff --git a/dom/ipc/nsIContentParent.idl b/dom/ipc/nsIContentParent.idl
new file mode 100644
index 000000000000..fb8fd0ff9524
--- /dev/null
+++ b/dom/ipc/nsIContentParent.idl
@@ -0,0 +1,11 @@
+#include "nsISupports.idl"
+
+webidl JSProcessActorParent;
+
+[scriptable, builtinclass, uuid(81fc08b9-c901-471f-ab0d-876362eba770)]
+interface nsIContentParent: nsISupports {
+    // Internal ID of the process.
+    readonly attribute unsigned long long childID;
+
+    JSProcessActorParent getActor(in ACString name);
+};
diff --git a/dom/ipc/nsIDOMProcessChild.idl b/dom/ipc/nsIDOMProcessChild.idl
deleted file mode 100644
index 91e060868efd..000000000000
--- a/dom/ipc/nsIDOMProcessChild.idl
+++ /dev/null
@@ -1,42 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim:set ts=2 sw=2 sts=2 et cindent: */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "nsISupports.idl"
-
-%{C++
-namespace mozilla {
-namespace dom {
-class ContentChild;
-} // namespace dom
-} // namespace mozilla
-%}
-[ptr] native ContentChildPtr(mozilla::dom::ContentChild);
-
-webidl JSProcessActorChild;
-
-/**
- * Child actor interface for a process which can host DOM content.
- *
- * Implemented by either `InProcessChild` for the parent process, or
- * `ContentChild` for a content process.
- */
-[scriptable, builtinclass, uuid(b0c6e5f3-02f1-4f11-a0af-336fc231f3bf)]
-interface nsIDOMProcessChild: nsISupports {
-  /**
-   * Internal child process ID. `0` is reserved for the parent process.
-   */
-  [infallible] readonly attribute unsigned long long childID;
-
-  /**
-   * Lookup a JSProcessActorChild managed by this interface by name.
-   */
-  JSProcessActorChild getActor(in ACString name);
-
-  /** Can the actor still send messages? */
-  [infallible] readonly attribute boolean canSend;
-
-  [notxpcom, nostdcall] ContentChildPtr AsContentChild();
-};
diff --git a/dom/ipc/nsIDOMProcessParent.idl b/dom/ipc/nsIDOMProcessParent.idl
deleted file mode 100644
index c105ec46d09a..000000000000
--- a/dom/ipc/nsIDOMProcessParent.idl
+++ /dev/null
@@ -1,42 +0,0 @@
-/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim:set ts=2 sw=2 sts=2 et cindent: */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "nsISupports.idl"
-
-%{C++
-namespace mozilla {
-namespace dom {
-class ContentParent;
-} // namespace dom
-} // namespace mozilla
-%}
-[ptr] native ContentParentPtr(mozilla::dom::ContentParent);
-
-webidl JSProcessActorParent;
-
-/**
- * Parent actor interface for a process which can host DOM content.
- *
- * Implemented by either `InProcessParent` for the parent process, or
- * `ContentParent` for a content process.
- */
-[scriptable, builtinclass, uuid(81fc08b9-c901-471f-ab0d-876362eba770)]
-interface nsIDOMProcessParent: nsISupports {
-  /**
-   * Internal child process ID. `0` is reserved for the parent process.
-   */
-  [infallible] readonly attribute unsigned long long childID;
-
-  /**
-   * Lookup a JSProcessActorParent managed by this interface by name.
-   */
-  JSProcessActorParent getActor(in ACString name);
-
-  /** Can the actor still send messages? */
-  [infallible] readonly attribute boolean canSend;
-
-  [notxpcom, nostdcall] ContentParentPtr AsContentParent();
-};
diff --git a/dom/ipc/tests/JSProcessActor/browser_getActor.js b/dom/ipc/tests/JSProcessActor/browser_getActor.js
index e972eaaac9a7..2a555acbc9f0 100644
--- a/dom/ipc/tests/JSProcessActor/browser_getActor.js
+++ b/dom/ipc/tests/JSProcessActor/browser_getActor.js
@@ -4,7 +4,7 @@
 
 declTest("getActor on both sides", {
   async test(browser) {
-    let parent = browser.browsingContext.currentWindowGlobal.domProcess;
+    let parent = browser.browsingContext.currentWindowGlobal.contentParent;
     ok(parent, "WindowGlobalParent should have value.");
     let actorParent = parent.getActor("TestProcessActor");
     is(
@@ -15,7 +15,7 @@ declTest("getActor on both sides", {
     is(
       actorParent.manager,
       parent,
-      "manager should match WindowGlobalParent.domProcess"
+      "manager should match WindowGlobalParent.contentParent"
     );
 
     ok(
@@ -24,7 +24,7 @@ declTest("getActor on both sides", {
     );
 
     await SpecialPowers.spawn(browser, [], async function() {
-      let child = ChromeUtils.domProcessChild;
+      let child = ChromeUtils.contentChild;
       ok(child, "WindowGlobalChild should have value.");
       let actorChild = child.getActor("TestProcessActor");
       is(
@@ -35,7 +35,7 @@ declTest("getActor on both sides", {
       is(
         actorChild.manager,
         child,
-        "manager should match ChromeUtils.domProcessChild."
+        "manager should match ChromeUtils.contentChild."
       );
 
       ok(
diff --git a/dom/ipc/tests/JSProcessActor/browser_observer_notification.js b/dom/ipc/tests/JSProcessActor/browser_observer_notification.js
index dfe92ad24079..a8b819eb412d 100644
--- a/dom/ipc/tests/JSProcessActor/browser_observer_notification.js
+++ b/dom/ipc/tests/JSProcessActor/browser_observer_notification.js
@@ -9,7 +9,7 @@ declTest("test observer triggering actor creation", {
       const TOPIC = "test-js-content-actor-child-observer";
       Services.obs.notifyObservers(content.window, TOPIC, "dataString");
 
-      let child = ChromeUtils.domProcessChild;
+      let child = ChromeUtils.contentChild;
       let actorChild = child.getActor("TestProcessActor");
       ok(actorChild, "JSProcessActorChild should have value.");
       ok(
@@ -29,7 +29,7 @@ declTest("test observers with null data", {
       const TOPIC = "test-js-content-actor-child-observer";
       Services.obs.notifyObservers(content.window, TOPIC);
 
-      let child = ChromeUtils.domProcessChild;
+      let child = ChromeUtils.contentChild;
       let actorChild = child.getActor("TestProcessActor");
       ok(actorChild, "JSProcessActorChild should have value.");
       let { subject, topic, data } = actorChild.lastObserved;
diff --git a/dom/ipc/tests/JSProcessActor/browser_sendAsyncMessage.js b/dom/ipc/tests/JSProcessActor/browser_sendAsyncMessage.js
index f81d4ddbeed4..2906f9d81ae6 100644
--- a/dom/ipc/tests/JSProcessActor/browser_sendAsyncMessage.js
+++ b/dom/ipc/tests/JSProcessActor/browser_sendAsyncMessage.js
@@ -4,12 +4,12 @@
 
 declTest("asyncMessage testing", {
   async test(browser) {
-    let parent = browser.browsingContext.currentWindowGlobal.domProcess;
+    let parent = browser.browsingContext.currentWindowGlobal.contentParent;
     let actorParent = parent.getActor("TestProcessActor");
     ok(actorParent, "JSProcessActorParent should have value.");
 
     await ContentTask.spawn(browser, {}, async function() {
-      let child = ChromeUtils.domProcessChild;
+      let child = ChromeUtils.contentChild;
       let actorChild = child.getActor("TestProcessActor");
       ok(actorChild, "JSProcessActorChild should have value.");
 
@@ -32,7 +32,7 @@ declTest("asyncMessage without both sides", {
     // If we don't create a parent actor, make sure the parent actor
     // gets created by having sent the message.
     await ContentTask.spawn(browser, {}, async function() {
-      let child = ChromeUtils.domProcessChild;
+      let child = ChromeUtils.contentChild;
       let actorChild = child.getActor("TestProcessActor");
       ok(actorChild, "JSProcessActorChild should have value.");
 
diff --git a/dom/ipc/tests/JSProcessActor/browser_sendQuery.js b/dom/ipc/tests/JSProcessActor/browser_sendQuery.js
index 69fe881367c4..99b7209f494d 100644
--- a/dom/ipc/tests/JSProcessActor/browser_sendQuery.js
+++ b/dom/ipc/tests/JSProcessActor/browser_sendQuery.js
@@ -23,7 +23,7 @@ function maybeAsyncStack(offset, column) {
 
 declTest("sendQuery Error", {
   async test(browser) {
-    let parent = browser.browsingContext.currentWindowGlobal.domProcess;
+    let parent = browser.browsingContext.currentWindowGlobal.contentParent;
     let actorParent = parent.getActor("TestProcessActor");
 
     let asyncStack = maybeAsyncStack(2, 8);
@@ -44,7 +44,7 @@ declTest("sendQuery Error", {
 
 declTest("sendQuery Exception", {
   async test(browser) {
-    let parent = browser.browsingContext.currentWindowGlobal.domProcess;
+    let parent = browser.browsingContext.currentWindowGlobal.contentParent;
     let actorParent = parent.getActor("TestProcessActor");
 
     let asyncStack = maybeAsyncStack(2, 8);
@@ -72,7 +72,7 @@ declTest("sendQuery Exception", {
 
 declTest("sendQuery testing", {
   async test(browser) {
-    let parent = browser.browsingContext.currentWindowGlobal.domProcess;
+    let parent = browser.browsingContext.currentWindowGlobal.contentParent;
     let actorParent = parent.getActor("TestProcessActor");
     ok(actorParent, "JSWindowActorParent should have value.");
 
diff --git a/dom/ipc/tests/JSWindowActor/browser_process_childid.js b/dom/ipc/tests/JSWindowActor/browser_process_childid.js
index 95e1a0c422a3..076419ba0bb5 100644
--- a/dom/ipc/tests/JSWindowActor/browser_process_childid.js
+++ b/dom/ipc/tests/JSWindowActor/browser_process_childid.js
@@ -8,18 +8,18 @@ declTest("test childid", {
   async test(browser) {
     let parent = browser.browsingContext.currentWindowGlobal;
     ok(
-      parent.domProcess.childID,
-      "parent domProcess.childID should have a value."
+      parent.contentParent.childID,
+      "parent contentParent.childID should have a value."
     );
     await SpecialPowers.spawn(
       browser,
-      [parent.domProcess.childID],
+      [parent.contentParent.childID],
       async function(parentChildID) {
         ok(
-          ChromeUtils.domProcessChild.childID,
+          ChromeUtils.contentChild.childID,
           "child process.childID should have a value."
         );
-        let childID = ChromeUtils.domProcessChild.childID;
+        let childID = ChromeUtils.contentChild.childID;
         is(parentChildID, childID);
       }
     );
diff --git a/ipc/glue/IPDLParamTraits.h b/ipc/glue/IPDLParamTraits.h
index f258bdcaf688..90d0baf37921 100644
--- a/ipc/glue/IPDLParamTraits.h
+++ b/ipc/glue/IPDLParamTraits.h
@@ -10,8 +10,6 @@
 #include "chrome/common/ipc_message_utils.h"
 #include "mozilla/UniquePtr.h"
 #include "mozilla/Variant.h"
-#include "mozilla/Tuple.h"
-#include "nsTArray.h"
 
 #include <type_traits>
 
diff --git a/dom/ipc/InProcessChild.h b/ipc/glue/InProcessChild.h
similarity index 68%
rename from dom/ipc/InProcessChild.h
rename to ipc/glue/InProcessChild.h
index 26d695148a50..f0f3645a75d8 100644
--- a/dom/ipc/InProcessChild.h
+++ b/ipc/glue/InProcessChild.h
@@ -4,19 +4,20 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#ifndef mozilla_dom_InProcessChild_h
-#define mozilla_dom_InProcessChild_h
+#ifndef mozilla_ipc_InProcessChild_h
+#define mozilla_ipc_InProcessChild_h
 
-#include "mozilla/dom/PInProcessChild.h"
-#include "mozilla/dom/JSProcessActorChild.h"
-#include "mozilla/dom/ProcessActor.h"
+#include "mozilla/ipc/PInProcessChild.h"
 #include "mozilla/StaticPtr.h"
-#include "nsIDOMProcessChild.h"
 
 namespace mozilla {
 namespace dom {
 class PWindowGlobalParent;
 class PWindowGlobalChild;
+}  // namespace dom
+
+namespace ipc {
+
 class InProcessParent;
 
 /**
@@ -27,15 +28,12 @@ class InProcessParent;
  * for async actors which want to communicate uniformly between Content->Chrome
  * and Chrome->Chrome situations.
  */
-class InProcessChild final : public nsIDOMProcessChild,
-                             public PInProcessChild,
-                             public ProcessActor {
+class InProcessChild final : public PInProcessChild {
  public:
   friend class InProcessParent;
   friend class PInProcessChild;
 
-  NS_DECL_ISUPPORTS
-  NS_DECL_NSIDOMPROCESSCHILD
+  NS_INLINE_DECL_REFCOUNTING(InProcessChild, final)
 
   // Get the singleton instance of this actor.
   static InProcessChild* Singleton();
@@ -45,9 +43,6 @@ class InProcessChild final : public nsIDOMProcessChild,
   // |nullptr|.
   static IProtocol* ParentActorFor(IProtocol* aActor);
 
-  const nsAString& GetRemoteType() const override { return VoidString(); }
-  JSActor::Type GetSide() override { return JSActor::Type::Child; }
-
  private:
   // NOTE: PInProcess lifecycle management is declared as staic methods and
   // state on InProcessParent, and implemented in InProcessImpl.cpp.
@@ -55,11 +50,9 @@ class InProcessChild final : public nsIDOMProcessChild,
   ~InProcessChild() = default;
 
   static StaticRefPtr<InProcessChild> sSingleton;
-
-  nsRefPtrHashtable<nsCStringHashKey, JSProcessActorChild> mProcessActors;
 };
 
-}  // namespace dom
+}  // namespace ipc
 }  // namespace mozilla
 
-#endif  // defined(mozilla_dom_InProcessChild_h)
+#endif  // defined(mozilla_ipc_InProcessChild_h)
diff --git a/dom/ipc/InProcessImpl.cpp b/ipc/glue/InProcessImpl.cpp
similarity index 61%
rename from dom/ipc/InProcessImpl.cpp
rename to ipc/glue/InProcessImpl.cpp
index b34ba95c1447..db5b8d3adceb 100644
--- a/dom/ipc/InProcessImpl.cpp
+++ b/ipc/glue/InProcessImpl.cpp
@@ -4,19 +4,16 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#include "mozilla/dom/InProcessParent.h"
-#include "mozilla/dom/InProcessChild.h"
-#include "mozilla/dom/JSProcessActorBinding.h"
+#include "mozilla/ipc/InProcessParent.h"
+#include "mozilla/ipc/InProcessChild.h"
 #include "nsIObserverService.h"
 #include "mozilla/Services.h"
 
-using namespace mozilla::ipc;
-
 // This file contains the implementation of core InProcess lifecycle management
 // facilities.
 
 namespace mozilla {
-namespace dom {
+namespace ipc {
 
 StaticRefPtr<InProcessParent> InProcessParent::sSingleton;
 StaticRefPtr<InProcessChild> InProcessChild::sSingleton;
@@ -118,118 +115,6 @@ void InProcessChild::ActorDestroy(ActorDestroyReason aWhy) {
   InProcessParent::Shutdown();
 }
 
-/////////////////////////
-// nsIDOMProcessParent //
-/////////////////////////
-
-NS_IMETHODIMP
-InProcessParent::GetChildID(uint64_t* aChildID) {
-  *aChildID = 0;
-  return NS_OK;
-}
-
-NS_IMETHODIMP
-InProcessParent::GetActor(const nsACString& aName,
-                          JSProcessActorParent** aActor) {
-  if (!CanSend()) {
-    return NS_ERROR_DOM_INVALID_STATE_ERR;
-  }
-
-  // Check if this actor has already been created, and return it if it has.
-  if (mProcessActors.Contains(aName)) {
-    RefPtr<JSProcessActorParent> actor(mProcessActors.Get(aName));
-    actor.forget(aActor);
-    return NS_OK;
-  }
-
-  // Otherwise, we want to create a new instance of this actor.
-  JS::RootedObject obj(RootingCx());
-  ErrorResult result;
-  ConstructActor(aName, &obj, result);
-  if (result.Failed()) {
-    return result.StealNSResult();
-  }
-
-  // Unwrap our actor to a JSProcessActorParent object.
-  RefPtr<JSProcessActorParent> actor;
-  nsresult rv = UNWRAP_OBJECT(JSProcessActorParent, &obj, actor);
-  if (NS_FAILED(rv)) {
-    return rv;
-  }
-
-  MOZ_RELEASE_ASSERT(!actor->Manager(),
-                     "mManager was already initialized once!");
-  actor->Init(aName, this);
-  mProcessActors.Put(aName, RefPtr{actor});
-  actor.forget(aActor);
-  return NS_OK;
-}
-
-NS_IMETHODIMP
-InProcessParent::GetCanSend(bool* aCanSend) {
-  *aCanSend = CanSend();
-  return NS_OK;
-}
-
-NS_IMETHODIMP_(ContentParent*)
-InProcessParent::AsContentParent() { return nullptr; }
-
-////////////////////////
-// nsIDOMProcessChild //
-////////////////////////
-
-NS_IMETHODIMP
-InProcessChild::GetChildID(uint64_t* aChildID) {
-  *aChildID = 0;
-  return NS_OK;
-}
-
-NS_IMETHODIMP
-InProcessChild::GetActor(const nsACString& aName,
-                         JSProcessActorChild** aActor) {
-  if (!CanSend()) {
-    return NS_ERROR_DOM_INVALID_STATE_ERR;
-  }
-
-  // Check if this actor has already been created, and return it if it has.
-  if (mProcessActors.Contains(aName)) {
-    RefPtr<JSProcessActorChild> actor(mProcessActors.Get(aName));
-    actor.forget(aActor);
-    return NS_OK;
-  }
-
-  // Otherwise, we want to create a new instance of this actor.
-  JS::RootedObject obj(RootingCx());
-  ErrorResult result;
-  ConstructActor(aName, &obj, result);
-  if (result.Failed()) {
-    return result.StealNSResult();
-  }
-
-  // Unwrap our actor to a JSProcessActorChild object.
-  RefPtr<JSProcessActorChild> actor;
-  nsresult rv = UNWRAP_OBJECT(JSProcessActorChild, &obj, actor);
-  if (NS_FAILED(rv)) {
-    return rv;
-  }
-
-  MOZ_RELEASE_ASSERT(!actor->Manager(),
-                     "mManager was already initialized once!");
-  actor->Init(aName, this);
-  mProcessActors.Put(aName, RefPtr{actor});
-  actor.forget(aActor);
-  return NS_OK;
-}
-
-NS_IMETHODIMP
-InProcessChild::GetCanSend(bool* aCanSend) {
-  *aCanSend = CanSend();
-  return NS_OK;
-}
-
-NS_IMETHODIMP_(ContentChild*)
-InProcessChild::AsContentChild() { return nullptr; }
-
 ////////////////////////////////
 // In-Process Actor Utilities //
 ////////////////////////////////
@@ -292,8 +177,7 @@ IProtocol* InProcessChild::ParentActorFor(IProtocol* aActor) {
   return GetOtherInProcessActor(aActor);
 }
 
-NS_IMPL_ISUPPORTS(InProcessParent, nsIDOMProcessParent, nsIObserver)
-NS_IMPL_ISUPPORTS(InProcessChild, nsIDOMProcessChild)
+NS_IMPL_ISUPPORTS(InProcessParent, nsIObserver)
 
-}  // namespace dom
+}  // namespace ipc
 }  // namespace mozilla
diff --git a/dom/ipc/InProcessParent.h b/ipc/glue/InProcessParent.h
similarity index 67%
rename from dom/ipc/InProcessParent.h
rename to ipc/glue/InProcessParent.h
index b30d6bf3f17e..2e3aa3553442 100644
--- a/dom/ipc/InProcessParent.h
+++ b/ipc/glue/InProcessParent.h
@@ -4,19 +4,20 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#ifndef mozilla_dom_InProcessParent_h
-#define mozilla_dom_InProcessParent_h
+#ifndef mozilla_ipc_InProcessParent_h
+#define mozilla_ipc_InProcessParent_h
 
-#include "mozilla/dom/PInProcessParent.h"
-#include "mozilla/dom/JSProcessActorParent.h"
-#include "mozilla/dom/ProcessActor.h"
+#include "mozilla/ipc/PInProcessParent.h"
 #include "mozilla/StaticPtr.h"
-#include "nsIDOMProcessParent.h"
 
 namespace mozilla {
 namespace dom {
 class PWindowGlobalParent;
 class PWindowGlobalChild;
+}  // namespace dom
+
+namespace ipc {
+
 class InProcessChild;
 
 /**
@@ -27,16 +28,12 @@ class InProcessChild;
  * for async actors which want to communicate uniformly between Content->Chrome
  * and Chrome->Chrome situations.
  */
-class InProcessParent final : public nsIDOMProcessParent,
-                              public nsIObserver,
-                              public PInProcessParent,
-                              public ProcessActor {
+class InProcessParent final : public nsIObserver, public PInProcessParent {
  public:
   friend class InProcessChild;
   friend class PInProcessParent;
 
   NS_DECL_ISUPPORTS
-  NS_DECL_NSIDOMPROCESSPARENT
   NS_DECL_NSIOBSERVER
 
   // Get the singleton instance of this actor.
@@ -47,9 +44,6 @@ class InProcessParent final : public nsIDOMProcessParent,
   // |nullptr|.
   static IProtocol* ChildActorFor(IProtocol* aActor);
 
-  const nsAString& GetRemoteType() const override { return VoidString(); };
-  JSActor::Type GetSide() override { return JSActor::Type::Parent; }
-
  private:
   // Lifecycle management is implemented in InProcessImpl.cpp
   virtual void ActorDestroy(ActorDestroyReason aWhy) override;
@@ -60,11 +54,9 @@ class InProcessParent final : public nsIDOMProcessParent,
 
   static StaticRefPtr<InProcessParent> sSingleton;
   static bool sShutdown;
-
-  nsRefPtrHashtable<nsCStringHashKey, JSProcessActorParent> mProcessActors;
 };
 
-}  // namespace dom
+}  // namespace ipc
 }  // namespace mozilla
 
-#endif  // defined(mozilla_dom_InProcessParent_h)
+#endif  // defined(mozilla_ipc_InProcessParent_h)
diff --git a/dom/ipc/PInProcess.ipdl b/ipc/glue/PInProcess.ipdl
similarity index 88%
rename from dom/ipc/PInProcess.ipdl
rename to ipc/glue/PInProcess.ipdl
index 6b14ae36638d..28d7d95b61ad 100644
--- a/dom/ipc/PInProcess.ipdl
+++ b/ipc/glue/PInProcess.ipdl
@@ -9,14 +9,14 @@ include protocol PWindowGlobal;
 include DOMTypes;
 
 namespace mozilla {
-namespace dom {
+namespace ipc {
 
 /**
  * PInProcess is intended for use as an alternative actor manager to PContent
  * for async actors which want to be used uniformly in both Content->Chrome and
  * Chrome->Chrome circumstances.
  *
- * `mozilla::dom::InProcess{Parent, Child}::Singleton()` should be used to get
+ * `mozilla::ipc::InProcess{Parent, Child}::Singleton()` should be used to get
  * an instance of this actor.
  */
 async refcounted protocol PInProcess
@@ -24,5 +24,5 @@ async refcounted protocol PInProcess
   manages PWindowGlobal;
 };
 
-} // namespace dom
+} // namespace ipc
 } // namespace mozilla
diff --git a/ipc/glue/moz.build b/ipc/glue/moz.build
index 21aab170c5ca..feb9281c00ba 100644
--- a/ipc/glue/moz.build
+++ b/ipc/glue/moz.build
@@ -29,6 +29,8 @@ EXPORTS.mozilla.ipc += [
     'GeckoChildProcessHost.h',
     'IdleSchedulerChild.h',
     'IdleSchedulerParent.h',
+    'InProcessChild.h',
+    'InProcessParent.h',
     'InputStreamUtils.h',
     'IOThreadChild.h',
     'IPCStreamAlloc.h',
@@ -153,6 +155,7 @@ UNIFIED_SOURCES += [
     'FileDescriptorUtils.cpp',
     'IdleSchedulerChild.cpp',
     'IdleSchedulerParent.cpp',
+    'InProcessImpl.cpp',
     'InputStreamUtils.cpp',
     'IPCMessageUtils.cpp',
     'IPCStreamChild.cpp',
@@ -213,6 +216,7 @@ IPDL_SOURCES = [
     'PChildToParentStream.ipdl',
     'PFileDescriptorSet.ipdl',
     'PIdleScheduler.ipdl',
+    'PInProcess.ipdl',
     'PParentToChildStream.ipdl',
     'ProtocolTypes.ipdlh',
     'URIParams.ipdlh',