Enable more layer_tree_host_unittest for LayerTreeHostRemote.

cc/blimp/layer_tree_host_remote.cc

Index: cc/blimp/layer_tree_host_remote.cc
diff --git a/cc/blimp/layer_tree_host_remote.cc b/cc/blimp/layer_tree_host_remote.cc
index 56418c88418a2725a4e77caa8a73e0f68c70bffc..3e94aac020223c6af259e7941ed01c40fd4543bb 100644
--- a/cc/blimp/layer_tree_host_remote.cc
+++ b/cc/blimp/layer_tree_host_remote.cc
@@ -487,10 +487,13 @@ void LayerTreeHostRemote::SerializeCurrentState(
                           inputs_only);
 
   // Serialize the dirty layers.
-  for (auto* layer : layer_tree_->LayersThatShouldPushProperties())
+  std::unordered_set<Layer*> layers_need_push_properties;
+  layers_need_push_properties.swap(
+      layer_tree_->LayersThatShouldPushProperties());

[Khushal, 2016/10/28 23:11:50]

Do you mind adding a small test for this in layer_tree_host_remote_unittest?

Create a tree with 3 layers or so and in the first frame, all layers would be
serialized. Then modify a single layer and make sure in the second frame only
that layer is serialized?

[xingliu, 2016/10/31 18:48:05]

Done, make sense. Also tweak UpdateTrackingRemoteCompositorBridge in
layer_tree_host_remote_unittest.cc, not sure if this is really needed.

+
+  for (auto* layer : layers_need_push_properties)
     layer->ToLayerPropertiesProto(
         layer_tree_host_proto->mutable_layer_updates(), inputs_only);
-  layer_tree_->LayersThatShouldPushProperties().clear();
 
   std::vector<PictureData> pictures =
       engine_picture_cache_->CalculateCacheUpdateAndFlush();