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 b7e0e7c405e9c5518d600b6b875f37ab72fbabca..dd6f38fa99418b63a46c1f603b2d92caa8217b85 100644
--- a/cc/thread_proxy.cc
+++ b/cc/thread_proxy.cc
@@ -50,6 +50,7 @@ ThreadProxy::ThreadProxy(LayerTreeHost* layerTreeHost, scoped_ptr<Thread> implTh
     , m_readbackRequestOnImplThread(0)
     , m_commitCompletionEventOnImplThread(0)
     , m_textureAcquisitionCompletionEventOnImplThread(0)
+    , m_pendingTreeActivationEventOnImplThread(0)
     , m_nextFrameIsNewlyCommittedFrameOnImplThread(false)
     , m_renderVSyncEnabled(layerTreeHost->settings().renderVSyncEnabled)
     , m_totalCommitCount(0)
@@ -643,6 +644,9 @@ void ThreadProxy::beginFrame(scoped_ptr<BeginFrameAndCommitState> beginFrameStat
 
     m_layerTreeHost->commitComplete();
     m_layerTreeHost->didBeginFrame();
+
+    if (m_layerTreeHost->settings().implSidePainting)
+        blockUntilPendingActivationIfNeeded();
 }
 
 void ThreadProxy::beginFrameCompleteOnImplThread(CompletionEvent* completion, ResourceUpdateQueue* rawQueue)
@@ -770,6 +774,14 @@ ScheduledActionDrawAndSwapResult ThreadProxy::scheduledActionDrawAndSwapInternal
     }
     m_layerTreeHostImpl->didDrawAllLayers(frame);
 
+    // Check for tree activation
+    if (m_pendingTreeActivationEventOnImplThread && !m_layerTreeHostImpl->pendingTree())
+    {
+        DCHECK(m_layerTreeHostImpl->settings().implSidePainting);
+        m_pendingTreeActivationEventOnImplThread->signal();
+        m_pendingTreeActivationEventOnImplThread = 0;
+    }
+
     // Check for a pending compositeAndReadback.
     if (m_readbackRequestOnImplThread) {
         m_readbackRequestOnImplThread->success = false;
@@ -1012,4 +1024,34 @@ void ThreadProxy::commitPendingOnImplThreadForTesting(CommitPendingRequest* requ
     request->completion.signal();
 }
 
+void ThreadProxy::blockUntilPendingActivationIfNeeded()
+{
+    DCHECK(isMainThread());
+    DCHECK(m_layerTreeHost->settings().implSidePainting);
+
+    if (!m_layerTreeHost->blocksPendingCommit())
+        return;
+
+    TRACE_EVENT0("cc", "ThreadProxy::blockUntilPendingActivationIfNeeded");
+    DebugScopedSetMainThreadBlocked mainThreadBlocked(this);
+    CompletionEvent completion;
+    Proxy::implThread()->postTask(base::Bind(&ThreadProxy::blockUntilPendingActivationOnImplThread, m_implThreadWeakPtr, &completion));
+    completion.wait();
+}
+
+void ThreadProxy::blockUntilPendingActivationOnImplThread(CompletionEvent* completion)
+{
+    DCHECK(isImplThread());
+    DCHECK(isMainThreadBlocked());
+    DCHECK(m_layerTreeHostImpl->settings().implSidePainting);
+    CHECK(!m_pendingTreeActivationEventOnImplThread);
+
+    if (!m_layerTreeHostImpl->pendingTree()) {
+        completion->signal();
+        return;
+    }
+
+    m_pendingTreeActivationEventOnImplThread = completion;
+}
+
 }  // namespace cc