Bug 1127270: Only acquire a hold on the compositor thread once the channel for a parent actor has been succesfully connected. r=nical

gfx/layers/ipc/CompositorParent.cpp

@@ -1636,7 +1636,6 @@ class CrossProcessCompositorParent final : public PCompositorParent,
 public:
   explicit CrossProcessCompositorParent(Transport* aTransport)
     : mTransport(aTransport)
-    , mCompositorThreadHolder(sCompositorThreadHolder)
     , mNotifyAfterRemotePaint(false)
   {
     MOZ_ASSERT(NS_IsMainThread());
@@ -1726,6 +1725,8 @@ public:
                     TimeStamp& aCompositeStart,
                     TimeStamp& aCompositeEnd);
 
+protected:
+  void OnChannelConnected(int32_t pid) override { mCompositorThreadHolder = sCompositorThreadHolder; }
 private:
   // Private destructor, to discourage deletion outside of Release():
   virtual ~CrossProcessCompositorParent();

gfx/layers/ipc/ImageBridgeParent.cpp

@@ -58,7 +58,6 @@ ImageBridgeParent::ImageBridgeParent(MessageLoop* aLoop,
   : mMessageLoop(aLoop)
   , mTransport(aTransport)
   , mSetChildThreadPriority(false)
-  , mCompositorThreadHolder(GetCompositorThreadHolder())
 {
   MOZ_ASSERT(NS_IsMainThread());
   sMainLoop = MessageLoop::current();
@@ -385,6 +384,12 @@ ImageBridgeParent::CloneToplevel(const InfallibleTArray<ProtocolFdMapping>& aFds
   return nullptr;
 }
 
+void
+ImageBridgeParent::OnChannelConnected(int32_t aPid)
+{
+  mCompositorThreadHolder = GetCompositorThreadHolder();
+}
+
 bool ImageBridgeParent::IsSameProcess() const
 {
   return OtherPid() == base::GetCurrentProcId();

gfx/layers/ipc/ImageBridgeParent.h

@@ -151,6 +151,9 @@ public:
                 base::ProcessHandle aPeerProcess,
                 mozilla::ipc::ProtocolCloneContext* aCtx) override;
 
+protected:
+  void OnChannelConnected(int32_t pid) override;
+
 private:
   void DeferredDestroy();
   MessageLoop* mMessageLoop;