diff --git a/dom/ipc/ContentChild.cpp b/dom/ipc/ContentChild.cpp
index e01b2bdd1aa6..6795a9450c8f 100644
--- a/dom/ipc/ContentChild.cpp
+++ b/dom/ipc/ContentChild.cpp
@@ -643,9 +643,8 @@ class nsGtkNativeInitRunnable : public Runnable {
   }
 };
 
-bool ContentChild::Init(MessageLoop* aIOLoop, base::ProcessId aParentPid,
-                        const char* aParentBuildID,
-                        UniquePtr<IPC::Channel> aChannel, uint64_t aChildID,
+bool ContentChild::Init(base::ProcessId aParentPid, const char* aParentBuildID,
+                        mozilla::ipc::ScopedPort aPort, uint64_t aChildID,
                         bool aIsForBrowser) {
 #ifdef MOZ_WIDGET_GTK
   // When running X11 only build we need to pass a display down
@@ -699,7 +698,7 @@ bool ContentChild::Init(MessageLoop* aIOLoop, base::ProcessId aParentPid,
     return false;
   }
 
-  if (!Open(std::move(aChannel), aParentPid, aIOLoop)) {
+  if (!Open(std::move(aPort), aParentPid)) {
     return false;
   }
   sSingleton = this;
diff --git a/dom/ipc/ContentChild.h b/dom/ipc/ContentChild.h
index f214a0ee2e8b..42abd0f5490b 100644
--- a/dom/ipc/ContentChild.h
+++ b/dom/ipc/ContentChild.h
@@ -119,9 +119,9 @@ class ContentChild final : public PContentChild,
       nsDocShellLoadState* aLoadState, bool* aWindowIsNew,
       BrowsingContext** aReturn);
 
-  bool Init(MessageLoop* aIOLoop, base::ProcessId aParentPid,
-            const char* aParentBuildID, UniquePtr<IPC::Channel> aChannel,
-            uint64_t aChildID, bool aIsForBrowser);
+  bool Init(base::ProcessId aParentPid, const char* aParentBuildID,
+            mozilla::ipc::ScopedPort aPort, uint64_t aChildID,
+            bool aIsForBrowser);
 
   void InitXPCOM(XPCOMInitData&& aXPCOMInit,
                  const mozilla::dom::ipc::StructuredCloneData& aInitialData);
diff --git a/dom/ipc/ContentParent.cpp b/dom/ipc/ContentParent.cpp
index 369d00a0fc46..37839936be6e 100644
--- a/dom/ipc/ContentParent.cpp
+++ b/dom/ipc/ContentParent.cpp
@@ -2570,16 +2570,14 @@ bool ContentParent::LaunchSubprocessResolve(bool aIsSync,
                                             ProcessPriority aPriority) {
   AUTO_PROFILER_LABEL("ContentParent::LaunchSubprocess::resolve", OTHER);
 
-  // Take the pending IPC channel. This channel will be used to open the raw IPC
-  // connection between this process and the launched content process.
-  UniquePtr<IPC::Channel> channel = mSubprocess->TakeChannel();
-  if (!channel) {
-    // We don't have a channel, so this method must've been called already.
+  if (mLaunchResolved) {
+    // We've already been called, return.
     MOZ_ASSERT(sCreatedFirstContentProcess);
     MOZ_ASSERT(!mPrefSerializer);
     MOZ_ASSERT(mLifecycleState != LifecycleState::LAUNCHING);
     return true;
   }
+  mLaunchResolved = true;
 
   // Now that communication with the child is complete, we can cleanup
   // the preference serializer.
@@ -2604,7 +2602,7 @@ bool ContentParent::LaunchSubprocessResolve(bool aIsSync,
 
   base::ProcessId procId =
       base::GetProcId(mSubprocess->GetChildProcessHandle());
-  Open(std::move(channel), procId);
+  Open(mSubprocess->TakeInitialPort(), procId);
 
   ContentProcessManager::GetSingleton()->AddContentProcess(this);
 
@@ -2732,6 +2730,7 @@ ContentParent::ContentParent(const nsACString& aRemoteType, int32_t aJSPluginID)
       mCalledKillHard(false),
       mCreatedPairedMinidumps(false),
       mShutdownPending(false),
+      mLaunchResolved(false),
       mIsRemoteInputEventQueueEnabled(false),
       mIsInputPriorityEventEnabled(false),
       mIsInPool(false),
diff --git a/dom/ipc/ContentParent.h b/dom/ipc/ContentParent.h
index ca3b3251a32f..b5065c21499e 100644
--- a/dom/ipc/ContentParent.h
+++ b/dom/ipc/ContentParent.h
@@ -1543,6 +1543,7 @@ class ContentParent final
   uint8_t mCalledKillHard : 1;
   uint8_t mCreatedPairedMinidumps : 1;
   uint8_t mShutdownPending : 1;
+  uint8_t mLaunchResolved : 1;
 
   // True if the input event queue on the main thread of the content process is
   // enabled.
diff --git a/dom/ipc/ContentProcess.cpp b/dom/ipc/ContentProcess.cpp
index 907f73b7e6da..d167b0a815d6 100644
--- a/dom/ipc/ContentProcess.cpp
+++ b/dom/ipc/ContentProcess.cpp
@@ -196,8 +196,8 @@ bool ContentProcess::Init(int aArgc, char* aArgv[]) {
     return false;
   }
 
-  mContent.Init(IOThreadChild::message_loop(), ParentPid(), *parentBuildID,
-                IOThreadChild::TakeChannel(), *childID, *isForBrowser);
+  mContent.Init(ParentPid(), *parentBuildID, IOThreadChild::TakeInitialPort(),
+                *childID, *isForBrowser);
 
   mXREEmbed.Start();
 #if (defined(XP_MACOSX)) && defined(MOZ_SANDBOX)
diff --git a/dom/media/gmp/GMPChild.cpp b/dom/media/gmp/GMPChild.cpp
index 7d48242f9025..f3f1bb8054c4 100644
--- a/dom/media/gmp/GMPChild.cpp
+++ b/dom/media/gmp/GMPChild.cpp
@@ -155,11 +155,11 @@ static bool GetPluginPaths(const nsAString& aPluginPath,
 #endif    // XP_MACOSX
 
 bool GMPChild::Init(const nsAString& aPluginPath, base::ProcessId aParentPid,
-                    MessageLoop* aIOLoop, UniquePtr<IPC::Channel> aChannel) {
+                    mozilla::ipc::ScopedPort aPort) {
   GMP_CHILD_LOG_DEBUG("%s pluginPath=%s", __FUNCTION__,
                       NS_ConvertUTF16toUTF8(aPluginPath).get());
 
-  if (NS_WARN_IF(!Open(std::move(aChannel), aParentPid, aIOLoop))) {
+  if (NS_WARN_IF(!Open(std::move(aPort), aParentPid))) {
     return false;
   }
 
diff --git a/dom/media/gmp/GMPChild.h b/dom/media/gmp/GMPChild.h
index 3c530d771a47..ddb774e0947b 100644
--- a/dom/media/gmp/GMPChild.h
+++ b/dom/media/gmp/GMPChild.h
@@ -26,7 +26,7 @@ class GMPChild : public PGMPChild {
   virtual ~GMPChild();
 
   bool Init(const nsAString& aPluginPath, base::ProcessId aParentPid,
-            MessageLoop* aIOLoop, UniquePtr<IPC::Channel> aChannel);
+            mozilla::ipc::ScopedPort aPort);
   MessageLoop* GMPMessageLoop();
 
   // Main thread only.
diff --git a/dom/media/gmp/GMPParent.cpp b/dom/media/gmp/GMPParent.cpp
index c50a2602866f..237937f9c9c2 100644
--- a/dom/media/gmp/GMPParent.cpp
+++ b/dom/media/gmp/GMPParent.cpp
@@ -280,7 +280,7 @@ nsresult GMPParent::LoadProcess() {
     mChildPid = base::GetProcId(mProcess->GetChildProcessHandle());
     GMP_PARENT_LOG_DEBUG("%s: Launched new child process", __FUNCTION__);
 
-    bool opened = Open(mProcess->TakeChannel(),
+    bool opened = Open(mProcess->TakeInitialPort(),
                        base::GetProcId(mProcess->GetChildProcessHandle()));
     if (!opened) {
       GMP_PARENT_LOG_DEBUG("%s: Failed to open channel to new child process",
diff --git a/dom/media/gmp/GMPProcessChild.cpp b/dom/media/gmp/GMPProcessChild.cpp
index cb2d1dadc442..3abfbd9ed612 100644
--- a/dom/media/gmp/GMPProcessChild.cpp
+++ b/dom/media/gmp/GMPProcessChild.cpp
@@ -41,8 +41,7 @@ bool GMPProcessChild::Init(int aArgc, char* aArgv[]) {
   BackgroundHangMonitor::Startup();
 
   return mPlugin.Init(pluginFilename, ParentPid(),
-                      IOThreadChild::message_loop(),
-                      IOThreadChild::TakeChannel());
+                      IOThreadChild::TakeInitialPort());
 }
 
 void GMPProcessChild::CleanUp() { BackgroundHangMonitor::Shutdown(); }
diff --git a/dom/media/ipc/RDDParent.cpp b/dom/media/ipc/RDDParent.cpp
index 4a4076874ad8..5be2f4024168 100644
--- a/dom/media/ipc/RDDParent.cpp
+++ b/dom/media/ipc/RDDParent.cpp
@@ -68,7 +68,7 @@ RDDParent* RDDParent::GetSingleton() {
 }
 
 bool RDDParent::Init(base::ProcessId aParentPid, const char* aParentBuildID,
-                     MessageLoop* aIOLoop, UniquePtr<IPC::Channel> aChannel) {
+                     mozilla::ipc::ScopedPort aPort) {
   // Initialize the thread manager before starting IPC. Otherwise, messages
   // may be posted to the main thread and we won't be able to process them.
   if (NS_WARN_IF(NS_FAILED(nsThreadManager::get().Init()))) {
@@ -76,7 +76,7 @@ bool RDDParent::Init(base::ProcessId aParentPid, const char* aParentBuildID,
   }
 
   // Now it's safe to start IPC.
-  if (NS_WARN_IF(!Open(std::move(aChannel), aParentPid, aIOLoop))) {
+  if (NS_WARN_IF(!Open(std::move(aPort), aParentPid))) {
     return false;
   }
 
diff --git a/dom/media/ipc/RDDParent.h b/dom/media/ipc/RDDParent.h
index 8f0e5ea73774..975e5c6a7d82 100644
--- a/dom/media/ipc/RDDParent.h
+++ b/dom/media/ipc/RDDParent.h
@@ -25,7 +25,7 @@ class RDDParent final : public PRDDParent {
   AsyncBlockers& AsyncShutdownService() { return mShutdownBlockers; }
 
   bool Init(base::ProcessId aParentPid, const char* aParentBuildID,
-            MessageLoop* aIOLoop, UniquePtr<IPC::Channel> aChannel);
+            mozilla::ipc::ScopedPort aPort);
 
   mozilla::ipc::IPCResult RecvInit(nsTArray<GfxVarUpdate>&& vars,
                                    const Maybe<ipc::FileDescriptor>& aBrokerFd,
diff --git a/dom/media/ipc/RDDProcessHost.cpp b/dom/media/ipc/RDDProcessHost.cpp
index 73c51526d757..c2a5b1da7995 100644
--- a/dom/media/ipc/RDDProcessHost.cpp
+++ b/dom/media/ipc/RDDProcessHost.cpp
@@ -167,8 +167,8 @@ void RDDProcessHost::InitAfterConnect(bool aSucceeded) {
   }
   mProcessToken = ++sRDDProcessTokenCounter;
   mRDDChild = MakeUnique<RDDChild>(this);
-  DebugOnly<bool> rv =
-      mRDDChild->Open(TakeChannel(), base::GetProcId(GetChildProcessHandle()));
+  DebugOnly<bool> rv = mRDDChild->Open(
+      TakeInitialPort(), base::GetProcId(GetChildProcessHandle()));
   MOZ_ASSERT(rv);
 
   // Only clear mPrefSerializer in the success case to avoid a
diff --git a/dom/media/ipc/RDDProcessImpl.cpp b/dom/media/ipc/RDDProcessImpl.cpp
index 08233e3b11e0..c077a382a484 100644
--- a/dom/media/ipc/RDDProcessImpl.cpp
+++ b/dom/media/ipc/RDDProcessImpl.cpp
@@ -80,8 +80,8 @@ bool RDDProcessImpl::Init(int aArgc, char* aArgv[]) {
     return false;
   }
 
-  return mRDD.Init(ParentPid(), parentBuildID, IOThreadChild::message_loop(),
-                   IOThreadChild::TakeChannel());
+  return mRDD.Init(ParentPid(), parentBuildID,
+                   IOThreadChild::TakeInitialPort());
 }
 
 void RDDProcessImpl::CleanUp() { NS_ShutdownXPCOM(nullptr); }
diff --git a/gfx/ipc/GPUParent.cpp b/gfx/ipc/GPUParent.cpp
index cff8730eb382..f0550e00b928 100644
--- a/gfx/ipc/GPUParent.cpp
+++ b/gfx/ipc/GPUParent.cpp
@@ -140,7 +140,7 @@ GPUParent* GPUParent::GetSingleton() {
 }
 
 bool GPUParent::Init(base::ProcessId aParentPid, const char* aParentBuildID,
-                     MessageLoop* aIOLoop, UniquePtr<IPC::Channel> aChannel) {
+                     mozilla::ipc::ScopedPort aPort) {
   // Initialize the thread manager before starting IPC. Otherwise, messages
   // may be posted to the main thread and we won't be able to process them.
   if (NS_WARN_IF(NS_FAILED(nsThreadManager::get().Init()))) {
@@ -148,7 +148,7 @@ bool GPUParent::Init(base::ProcessId aParentPid, const char* aParentBuildID,
   }
 
   // Now it's safe to start IPC.
-  if (NS_WARN_IF(!Open(std::move(aChannel), aParentPid, aIOLoop))) {
+  if (NS_WARN_IF(!Open(std::move(aPort), aParentPid))) {
     return false;
   }
 
diff --git a/gfx/ipc/GPUParent.h b/gfx/ipc/GPUParent.h
index 27daf79af318..b5cf376bcd23 100644
--- a/gfx/ipc/GPUParent.h
+++ b/gfx/ipc/GPUParent.h
@@ -37,7 +37,7 @@ class GPUParent final : public PGPUParent {
   static bool MaybeFlushMemory();
 
   bool Init(base::ProcessId aParentPid, const char* aParentBuildID,
-            MessageLoop* aIOLoop, UniquePtr<IPC::Channel> aChannel);
+            mozilla::ipc::ScopedPort aPort);
   void NotifyDeviceReset();
 
   already_AddRefed<PAPZInputBridgeParent> AllocPAPZInputBridgeParent(
diff --git a/gfx/ipc/GPUProcessHost.cpp b/gfx/ipc/GPUProcessHost.cpp
index 206cb6c84825..684a4f9cf041 100644
--- a/gfx/ipc/GPUProcessHost.cpp
+++ b/gfx/ipc/GPUProcessHost.cpp
@@ -139,7 +139,7 @@ void GPUProcessHost::InitAfterConnect(bool aSucceeded) {
     mProcessToken = ++sProcessTokenCounter;
     mGPUChild = MakeUnique<GPUChild>(this);
     DebugOnly<bool> rv = mGPUChild->Open(
-        TakeChannel(), base::GetProcId(GetChildProcessHandle()));
+        TakeInitialPort(), base::GetProcId(GetChildProcessHandle()));
     MOZ_ASSERT(rv);
 
     mGPUChild->Init();
diff --git a/gfx/ipc/GPUProcessImpl.cpp b/gfx/ipc/GPUProcessImpl.cpp
index 8c9fc37c665e..296f6a4a77a0 100644
--- a/gfx/ipc/GPUProcessImpl.cpp
+++ b/gfx/ipc/GPUProcessImpl.cpp
@@ -73,8 +73,8 @@ bool GPUProcessImpl::Init(int aArgc, char* aArgv[]) {
     return false;
   }
 
-  return mGPU.Init(ParentPid(), parentBuildID, IOThreadChild::message_loop(),
-                   IOThreadChild::TakeChannel());
+  return mGPU.Init(ParentPid(), parentBuildID,
+                   IOThreadChild::TakeInitialPort());
 }
 
 void GPUProcessImpl::CleanUp() { NS_ShutdownXPCOM(nullptr); }
diff --git a/gfx/vr/ipc/VRParent.cpp b/gfx/vr/ipc/VRParent.cpp
index 3a5a5d9b49ab..6a78a5700b68 100644
--- a/gfx/vr/ipc/VRParent.cpp
+++ b/gfx/vr/ipc/VRParent.cpp
@@ -132,7 +132,7 @@ void VRParent::ActorDestroy(ActorDestroyReason aWhy) {
 }
 
 bool VRParent::Init(base::ProcessId aParentPid, const char* aParentBuildID,
-                    MessageLoop* aIOLoop, UniquePtr<IPC::Channel> aChannel) {
+                    mozilla::ipc::ScopedPort aPort) {
   // Initialize the thread manager before starting IPC. Otherwise, messages
   // may be posted to the main thread and we won't be able to process them.
   if (NS_WARN_IF(NS_FAILED(nsThreadManager::get().Init()))) {
@@ -140,7 +140,7 @@ bool VRParent::Init(base::ProcessId aParentPid, const char* aParentBuildID,
   }
 
   // Now it's safe to start IPC.
-  if (NS_WARN_IF(!Open(std::move(aChannel), aParentPid, aIOLoop))) {
+  if (NS_WARN_IF(!Open(std::move(aPort), aParentPid))) {
     return false;
   }
 
diff --git a/gfx/vr/ipc/VRParent.h b/gfx/vr/ipc/VRParent.h
index 36c0743ba5c2..d5de99cac5ce 100644
--- a/gfx/vr/ipc/VRParent.h
+++ b/gfx/vr/ipc/VRParent.h
@@ -25,7 +25,7 @@ class VRParent final : public PVRParent {
   explicit VRParent();
 
   bool Init(base::ProcessId aParentPid, const char* aParentBuildID,
-            MessageLoop* aIOLoop, UniquePtr<IPC::Channel> aChannel);
+            mozilla::ipc::ScopedPort aPort);
   virtual void ActorDestroy(ActorDestroyReason aWhy) override;
   bool GetOpenVRControllerActionPath(nsCString* aPath);
   bool GetOpenVRControllerManifestPath(VRControllerType aType,
diff --git a/gfx/vr/ipc/VRProcessChild.cpp b/gfx/vr/ipc/VRProcessChild.cpp
index 700a5519652e..4da047f7afea 100644
--- a/gfx/vr/ipc/VRProcessChild.cpp
+++ b/gfx/vr/ipc/VRProcessChild.cpp
@@ -72,8 +72,7 @@ bool VRProcessChild::Init(int aArgc, char* aArgv[]) {
   }
 
   sVRParent = new VRParent();
-  sVRParent->Init(ParentPid(), parentBuildID, IOThreadChild::message_loop(),
-                  IOThreadChild::TakeChannel());
+  sVRParent->Init(ParentPid(), parentBuildID, IOThreadChild::TakeInitialPort());
 
   return true;
 }
diff --git a/gfx/vr/ipc/VRProcessParent.cpp b/gfx/vr/ipc/VRProcessParent.cpp
index 8bae87631918..377e2bea99a2 100644
--- a/gfx/vr/ipc/VRProcessParent.cpp
+++ b/gfx/vr/ipc/VRProcessParent.cpp
@@ -157,8 +157,8 @@ bool VRProcessParent::InitAfterConnect(bool aSucceeded) {
 
     mVRChild = MakeUnique<VRChild>(this);
 
-    DebugOnly<bool> rv =
-        mVRChild->Open(TakeChannel(), base::GetProcId(GetChildProcessHandle()));
+    DebugOnly<bool> rv = mVRChild->Open(
+        TakeInitialPort(), base::GetProcId(GetChildProcessHandle()));
     MOZ_ASSERT(rv);
 
     mVRChild->Init();
diff --git a/ipc/ipdl/test/cxx/IPDLUnitTestProcessChild.cpp b/ipc/ipdl/test/cxx/IPDLUnitTestProcessChild.cpp
index d2a1f9872ae4..7683808535dd 100644
--- a/ipc/ipdl/test/cxx/IPDLUnitTestProcessChild.cpp
+++ b/ipc/ipdl/test/cxx/IPDLUnitTestProcessChild.cpp
@@ -16,6 +16,7 @@ namespace mozilla {
 namespace _ipdltest {
 
 bool IPDLUnitTestProcessChild::Init(int aArgc, char* aArgv[]) {
+  // FIXME(nika): this is quite clearly broken and needs to be fixed.
   IPDLUnitTestChildInit(IOThreadChild::TakeChannel(), ParentPid(),
                         IOThreadChild::message_loop());
 
diff --git a/netwerk/ipc/SocketProcessChild.cpp b/netwerk/ipc/SocketProcessChild.cpp
index 3e9297632a7e..b4a3d71e5e8d 100644
--- a/netwerk/ipc/SocketProcessChild.cpp
+++ b/netwerk/ipc/SocketProcessChild.cpp
@@ -98,12 +98,12 @@ void CGSShutdownServerConnections();
 #endif
 
 bool SocketProcessChild::Init(base::ProcessId aParentPid,
-                              const char* aParentBuildID, MessageLoop* aIOLoop,
-                              UniquePtr<IPC::Channel> aChannel) {
+                              const char* aParentBuildID,
+                              mozilla::ipc::ScopedPort aPort) {
   if (NS_WARN_IF(NS_FAILED(nsThreadManager::get().Init()))) {
     return false;
   }
-  if (NS_WARN_IF(!Open(std::move(aChannel), aParentPid, aIOLoop))) {
+  if (NS_WARN_IF(!Open(std::move(aPort), aParentPid))) {
     return false;
   }
   // This must be sent before any IPDL message, which may hit sentinel
diff --git a/netwerk/ipc/SocketProcessChild.h b/netwerk/ipc/SocketProcessChild.h
index fc5004ce86fc..e5c1e4f23eab 100644
--- a/netwerk/ipc/SocketProcessChild.h
+++ b/netwerk/ipc/SocketProcessChild.h
@@ -35,7 +35,7 @@ class SocketProcessChild final
   static SocketProcessChild* GetSingleton();
 
   bool Init(base::ProcessId aParentPid, const char* aParentBuildID,
-            MessageLoop* aIOLoop, UniquePtr<IPC::Channel> aChannel);
+            mozilla::ipc::ScopedPort aPort);
 
   void ActorDestroy(ActorDestroyReason aWhy) override;
 
diff --git a/netwerk/ipc/SocketProcessHost.cpp b/netwerk/ipc/SocketProcessHost.cpp
index 6dc5977c2a54..f35d369a17cb 100644
--- a/netwerk/ipc/SocketProcessHost.cpp
+++ b/netwerk/ipc/SocketProcessHost.cpp
@@ -143,7 +143,7 @@ void SocketProcessHost::InitAfterConnect(bool aSucceeded) {
 
   mSocketProcessParent = MakeUnique<SocketProcessParent>(this);
   DebugOnly<bool> rv = mSocketProcessParent->Open(
-      TakeChannel(), base::GetProcId(GetChildProcessHandle()));
+      TakeInitialPort(), base::GetProcId(GetChildProcessHandle()));
   MOZ_ASSERT(rv);
 
   SocketPorcessInitAttributes attributes;
diff --git a/netwerk/ipc/SocketProcessImpl.cpp b/netwerk/ipc/SocketProcessImpl.cpp
index ad539c67dcfb..a442ead33650 100644
--- a/netwerk/ipc/SocketProcessImpl.cpp
+++ b/netwerk/ipc/SocketProcessImpl.cpp
@@ -105,8 +105,7 @@ bool SocketProcessImpl::Init(int aArgc, char* aArgv[]) {
   }
 
   return mSocketProcessChild.Init(ParentPid(), parentBuildID,
-                                  IOThreadChild::message_loop(),
-                                  IOThreadChild::TakeChannel());
+                                  IOThreadChild::TakeInitialPort());
 }
 
 void SocketProcessImpl::CleanUp() { mSocketProcessChild.CleanUp(); }
diff --git a/security/sandbox/win/src/remotesandboxbroker/RemoteSandboxBrokerChild.cpp b/security/sandbox/win/src/remotesandboxbroker/RemoteSandboxBrokerChild.cpp
index f14b0b2fb400..367590685cd9 100644
--- a/security/sandbox/win/src/remotesandboxbroker/RemoteSandboxBrokerChild.cpp
+++ b/security/sandbox/win/src/remotesandboxbroker/RemoteSandboxBrokerChild.cpp
@@ -22,9 +22,8 @@ RemoteSandboxBrokerChild::RemoteSandboxBrokerChild() {
 RemoteSandboxBrokerChild::~RemoteSandboxBrokerChild() {}
 
 bool RemoteSandboxBrokerChild::Init(base::ProcessId aParentPid,
-                                    MessageLoop* aIOLoop,
-                                    UniquePtr<IPC::Channel> aChannel) {
-  if (NS_WARN_IF(!Open(std::move(aChannel), aParentPid, aIOLoop))) {
+                                    mozilla::ipc::ScopedPort aPort) {
+  if (NS_WARN_IF(!Open(std::move(aPort), aParentPid))) {
     return false;
   }
   CrashReporterClient::InitSingleton(this);
diff --git a/security/sandbox/win/src/remotesandboxbroker/RemoteSandboxBrokerChild.h b/security/sandbox/win/src/remotesandboxbroker/RemoteSandboxBrokerChild.h
index cf42ba37ca1e..5d82d065d55f 100644
--- a/security/sandbox/win/src/remotesandboxbroker/RemoteSandboxBrokerChild.h
+++ b/security/sandbox/win/src/remotesandboxbroker/RemoteSandboxBrokerChild.h
@@ -18,8 +18,7 @@ class RemoteSandboxBrokerChild : public PRemoteSandboxBrokerChild {
  public:
   RemoteSandboxBrokerChild();
   virtual ~RemoteSandboxBrokerChild();
-  bool Init(base::ProcessId aParentPid, MessageLoop* aIOLoop,
-            UniquePtr<IPC::Channel> aChannel);
+  bool Init(base::ProcessId aParentPid, mozilla::ipc::ScopedPort aPort);
 
  private:
   mozilla::ipc::IPCResult AnswerLaunchApp(LaunchParameters&& aParams,
diff --git a/security/sandbox/win/src/remotesandboxbroker/RemoteSandboxBrokerParent.cpp b/security/sandbox/win/src/remotesandboxbroker/RemoteSandboxBrokerParent.cpp
index f59421d45473..faafc21a2ce7 100644
--- a/security/sandbox/win/src/remotesandboxbroker/RemoteSandboxBrokerParent.cpp
+++ b/security/sandbox/win/src/remotesandboxbroker/RemoteSandboxBrokerParent.cpp
@@ -27,7 +27,7 @@ RefPtr<GenericPromise> RemoteSandboxBrokerParent::Launch(
   // Note: we rely on the caller to keep this instance alive while we launch
   // the process, so that these closures point to valid memory.
   auto resolve = [this](base::ProcessHandle handle) {
-    mOpened = Open(mProcess->TakeChannel(), base::GetProcId(handle));
+    mOpened = Open(mProcess->TakeInitialPort(), base::GetProcId(handle));
     if (!mOpened) {
       mProcess->Destroy();
       mProcess = nullptr;
diff --git a/security/sandbox/win/src/remotesandboxbroker/RemoteSandboxBrokerProcessChild.cpp b/security/sandbox/win/src/remotesandboxbroker/RemoteSandboxBrokerProcessChild.cpp
index a2628ebd4ca6..c9a3ac8ecb5c 100644
--- a/security/sandbox/win/src/remotesandboxbroker/RemoteSandboxBrokerProcessChild.cpp
+++ b/security/sandbox/win/src/remotesandboxbroker/RemoteSandboxBrokerProcessChild.cpp
@@ -21,8 +21,8 @@ RemoteSandboxBrokerProcessChild::~RemoteSandboxBrokerProcessChild() {}
 
 bool RemoteSandboxBrokerProcessChild::Init(int aArgc, char* aArgv[]) {
   BackgroundHangMonitor::Startup();
-  return mSandboxBrokerChild.Init(ParentPid(), IOThreadChild::message_loop(),
-                                  IOThreadChild::TakeChannel());
+  return mSandboxBrokerChild.Init(ParentPid(),
+                                  IOThreadChild::TakeInitialPort());
 }
 
 void RemoteSandboxBrokerProcessChild::CleanUp() {