cc: Block commit on activate by setting a flag on LayerTreeHost.

cc/layers/tiled_layer.cc

Index: cc/layers/tiled_layer.cc
diff --git a/cc/layers/tiled_layer.cc b/cc/layers/tiled_layer.cc
index 556b823147a5c8cf67c0432c3a4076bafbd31a5c..2d812e8933b04dfc525a5e99f0b89032a21f9b6b 100644
--- a/cc/layers/tiled_layer.cc
+++ b/cc/layers/tiled_layer.cc
@@ -235,8 +235,6 @@ void TiledLayer::PushPropertiesTo(LayerImpl* layer) {
   needs_push_properties_ = true;
 }
 
-bool TiledLayer::BlocksPendingCommit() const { return true; }
-
 PrioritizedResourceManager* TiledLayer::ResourceManager() {
   if (!layer_tree_host())
     return NULL;
@@ -731,6 +729,10 @@ bool TiledLayer::Update(ResourceUpdateQueue* queue,
                         const OcclusionTracker* occlusion) {
   DCHECK(!skips_draw_ && !failed_update_);  // Did ResetUpdateState get skipped?
 
+  // Tiled layer always causes commits to wait for activation, as it does
+  // not support pending trees.
+  SetNextCommitWaitsForActivation();
+
   bool updated = false;
 
   {