Bug 1435282 - Don't force the render transaction to happen immediately if we're doing an async flush. r=sotaro

This splits the FlushRendering function into sync and async versions
just for a bit more clarity. In the async version we don't want to set
the mForceRendering flag at all because we don't need to force a
rendering - if there is one already pending then that's good enough. And
anyway in practice the async version seems to only ever be invoked by
CompositorBridgeParent::SetTestSampleTime which I'll be changing in the
next patch.

MozReview-Commit-ID: 4cdU0U5B1pp

--HG--
extra : rebase_source : d7842844fca758d53121e3326d8da7fb7592ad8b

gfx/layers/ipc/CompositorBridgeParent.cpp

@@ -542,7 +542,7 @@ mozilla::ipc::IPCResult
 CompositorBridgeParent::RecvFlushRendering()
 {
   if (mOptions.UseWebRender()) {
-    mWrBridge->FlushRendering(/* aIsSync */ true);
+    mWrBridge->FlushRendering();
     return IPC_OK();
   }
 
@@ -557,7 +557,7 @@ mozilla::ipc::IPCResult
 CompositorBridgeParent::RecvFlushRenderingAsync()
 {
   if (mOptions.UseWebRender()) {
-    mWrBridge->FlushRendering(/* aIsSync */ false);
+    mWrBridge->FlushRenderingAsync();
     return IPC_OK();
   }
 
@@ -1289,7 +1289,7 @@ CompositorBridgeParent::SetTestSampleTime(const uint64_t& aId,
   mTestTime = aTime;
 
   if (mWrBridge) {
-    mWrBridge->FlushRendering(/*aIsSync*/ false);
+    mWrBridge->FlushRenderingAsync();
     return true;
   }
 

gfx/layers/wr/WebRenderBridgeParent.cpp

@@ -1338,7 +1338,7 @@ WebRenderBridgeParent::ScheduleGenerateFrame()
 }
 
 void
-WebRenderBridgeParent::FlushRendering(bool aIsSync)
+WebRenderBridgeParent::FlushRendering()
 {
   if (mDestroyed) {
     return;
@@ -1346,13 +1346,21 @@ WebRenderBridgeParent::FlushRendering(bool aIsSync)
 
   mForceRendering = true;
   if (mCompositorScheduler->FlushPendingComposite()) {
-    if (aIsSync) {
     mApi->WaitFlushed();
   }
-  }
   mForceRendering = false;
 }
 
+void
+WebRenderBridgeParent::FlushRenderingAsync()
+{
+  if (mDestroyed) {
+    return;
+  }
+
+  mCompositorScheduler->FlushPendingComposite();
+}
+
 void
 WebRenderBridgeParent::Pause()
 {

gfx/layers/wr/WebRenderBridgeParent.h

@@ -172,7 +172,8 @@ public:
   void UpdateAPZ(bool aUpdateHitTestingTree);
   const WebRenderScrollData& GetScrollData() const;
 
-  void FlushRendering(bool aIsSync);
+  void FlushRendering();
+  void FlushRenderingAsync();
 
   /**
    * Schedule generating WebRender frame definitely at next composite timing.