cc: Block the main thread for texture layers during impl-side painting

cc/thread_proxy.cc

Index: cc/thread_proxy.cc
diff --git a/cc/thread_proxy.cc b/cc/thread_proxy.cc
index b2f86c938124d4815c4ec7a7cd0714d938ba4223..3a43702fdb612755c7841d1ba02e3d35d21e0023 100644
--- a/cc/thread_proxy.cc
+++ b/cc/thread_proxy.cc
@@ -719,8 +719,17 @@ void ThreadProxy::scheduledActionCommit()
 
     m_nextFrameIsNewlyCommittedFrameOnImplThread = true;
 
-    m_commitCompletionEventOnImplThread->signal();
-    m_commitCompletionEventOnImplThread = 0;
+    if (m_layerTreeHost->settings().implSidePainting && m_layerTreeHost->blocksPendingCommit())
+    {
+        // For some layer types in impl-side painting, the commit is held until
+        // the pending tree is activated.
+        TRACE_EVENT_INSTANT0("cc", "HoldCommit");
+    }
+    else
+    {
+        m_commitCompletionEventOnImplThread->signal();
+        m_commitCompletionEventOnImplThread = 0;
+    }
 
     // SetVisible kicks off the next scheduler action, so this must be last.
     m_schedulerOnImplThread->setVisible(m_layerTreeHostImpl->visible());
@@ -774,6 +783,15 @@ ScheduledActionDrawAndSwapResult ThreadProxy::scheduledActionDrawAndSwapInternal
     }
     m_layerTreeHostImpl->didDrawAllLayers(frame);
 
+    // Check for tree activation.
+    if (m_commitCompletionEventOnImplThread && !m_layerTreeHostImpl->pendingTree())
+    {
+        TRACE_EVENT_INSTANT0("cc", "ReleaseCommitbyActivation");
+        DCHECK(m_layerTreeHostImpl->settings().implSidePainting);
+        m_commitCompletionEventOnImplThread->signal();
+        m_commitCompletionEventOnImplThread = 0;
+    }
+
     // Check for a pending compositeAndReadback.
     if (m_readbackRequestOnImplThread) {
         m_readbackRequestOnImplThread->success = false;