Bug 1771234 - Make it easier to use a specific serial event target when binding an actor, r=ipc-reviewers,mccr8

Differential Revision: https://phabricator.services.mozilla.com/D147381

ipc/glue/Endpoint.h

@@ -98,11 +98,16 @@ class Endpoint {
 
   // This method binds aActor to this endpoint. After this call, the actor can
   // be used to send and receive messages. The endpoint becomes invalid.
-  bool Bind(PFooSide* aActor) {
+  //
+  // If specified, aEventTarget is the target the actor will be bound to, and
+  // must be on the current thread. Otherwise, GetCurrentSerialEventTarget() is
+  // used.
+  bool Bind(PFooSide* aActor, nsISerialEventTarget* aEventTarget = nullptr) {
     MOZ_RELEASE_ASSERT(IsValid());
     MOZ_RELEASE_ASSERT(mMyPid == base::kInvalidProcessId ||
                        mMyPid == base::GetCurrentProcId());
-    return aActor->Open(std::move(mPort), mOtherPid);
+    MOZ_RELEASE_ASSERT(!aEventTarget || aEventTarget->IsOnCurrentThread());
+    return aActor->Open(std::move(mPort), mOtherPid, aEventTarget);
   }
 
   bool IsValid() const { return mPort.IsValid(); }

ipc/glue/ProtocolUtils.cpp

@@ -598,9 +598,10 @@ void IToplevelProtocol::SetOtherProcessId(base::ProcessId aOtherPid) {
   mOtherPid = aOtherPid;
 }
 
-bool IToplevelProtocol::Open(ScopedPort aPort, base::ProcessId aOtherPid) {
+bool IToplevelProtocol::Open(ScopedPort aPort, base::ProcessId aOtherPid,
+                             nsISerialEventTarget* aEventTarget) {
   SetOtherProcessId(aOtherPid);
-  return GetIPCChannel()->Open(std::move(aPort), mSide);
+  return GetIPCChannel()->Open(std::move(aPort), mSide, aEventTarget);
 }
 
 bool IToplevelProtocol::Open(IToplevelProtocol* aTarget,

ipc/glue/ProtocolUtils.h

@@ -417,7 +417,8 @@ class IToplevelProtocol : public IProtocol {
   virtual void OnChannelError() = 0;
   virtual void ProcessingError(Result aError, const char* aMsgName) {}
 
-  bool Open(ScopedPort aPort, base::ProcessId aOtherPid);
+  bool Open(ScopedPort aPort, base::ProcessId aOtherPid,
+            nsISerialEventTarget* aEventTarget = nullptr);
 
   bool Open(IToplevelProtocol* aTarget, nsISerialEventTarget* aEventTarget,
             mozilla::ipc::Side aSide = mozilla::ipc::UnknownSide);