Bug 1432635 - When advancing the test time, trigger a rendering flush to WR. r=sotaro

MozReview-Commit-ID: UtqGoOnobm

--HG--
extra : rebase_source : e3f3f135138014a4ed8c4bed23cca18c146995c1

gfx/layers/ipc/CompositorBridgeParent.cpp

@@ -1288,6 +1288,8 @@ bool
 CompositorBridgeParent::SetTestSampleTime(const uint64_t& aId,
                                           const TimeStamp& aTime)
 {
+  MOZ_ASSERT(CompositorThreadHolder::IsInCompositorThread());
+
   if (aTime.IsNull()) {
     return false;
   }
@@ -1295,6 +1297,11 @@ CompositorBridgeParent::SetTestSampleTime(const uint64_t& aId,
   mIsTesting = true;
   mTestTime = aTime;
 
+  if (mWrBridge) {
+    mWrBridge->FlushRendering(/*aIsSync*/ false);
+    return true;
+  }
+
   bool testComposite = mCompositionManager &&
                        mCompositorScheduler->NeedsComposite();