Setup LayerTree class, refactor 2 functions from LayerTreeHost to it.

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index cd025356975a3d31838bd9bf74d581cd7f189f1b..743836be685f3193c266ed6cd7e07824faa8002b 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -44,6 +44,7 @@
 #include "cc/layers/layer_proto_converter.h"
 #include "cc/layers/painted_scrollbar_layer.h"
 #include "cc/proto/gfx_conversions.h"
+#include "cc/proto/layer_tree.pb.h"
 #include "cc/proto/layer_tree_host.pb.h"
 #include "cc/resources/ui_resource_request.h"
 #include "cc/scheduler/begin_frame_source.h"
@@ -251,7 +252,8 @@ LayerTreeHost::LayerTreeHost(InitParams* params, CompositorMode mode)
       task_graph_runner_(params->task_graph_runner),
       image_serialization_processor_(params->image_serialization_processor),
       surface_client_id_(0u),
-      next_surface_sequence_(1u) {
+      next_surface_sequence_(1u),
+      layer_tree_() {

[Khushal, 2016/07/18 16:59:33]

Don't need to initialize it for a default ctor.

[xingliu, 2016/07/19 22:47:38]

Done.

   DCHECK(task_graph_runner_);
 
   DCHECK(animation_host_);
@@ -1345,20 +1347,20 @@ void LayerTreeHost::RemoveFromElementMap(Layer* layer) {
 }
 
 void LayerTreeHost::AddLayerShouldPushProperties(Layer* layer) {

[Khushal, 2016/07/18 16:59:33]

Why do we still need these methods on the host? This is being done in the
LayerTree now.

You should move all of the methods below for maintaining the LayerIdMap and
tracking which layers should push properties to the LayerTree and move all
accesses directly to it.

layer_tree_host->GetLayerTree()->RegisterLayer(layer).

[xingliu, 2016/07/19 22:47:38]

Done.

-  layers_that_should_push_properties_.insert(layer);
+  layer_tree_.AddLayerShouldPushProperties(layer);
 }
 
 void LayerTreeHost::RemoveLayerShouldPushProperties(Layer* layer) {
-  layers_that_should_push_properties_.erase(layer);
+  layer_tree_.RemoveLayerShouldPushProperties(layer);
 }
 
 std::unordered_set<Layer*>& LayerTreeHost::LayersThatShouldPushProperties() {
-  return layers_that_should_push_properties_;
+  return layer_tree_.layers_that_should_push_properties();
 }
 
 bool LayerTreeHost::LayerNeedsPushPropertiesForTesting(Layer* layer) {
-  return layers_that_should_push_properties_.find(layer) !=
-         layers_that_should_push_properties_.end();
+  const LayerSet& layers = layer_tree_.layers_that_should_push_properties();
+  return layers.find(layer) != layers.end();
 }
 
 void LayerTreeHost::RegisterLayer(Layer* layer) {
@@ -1378,7 +1380,8 @@ void LayerTreeHost::UnregisterLayer(Layer* layer) {
     animation_host_->UnregisterElement(layer->element_id(),
                                        ElementListType::ACTIVE);
   }
-  RemoveLayerShouldPushProperties(layer);
+
+  layer_tree_.RemoveLayerShouldPushProperties(layer);
   layer_id_map_.erase(layer->id());
 }
 
@@ -1540,8 +1543,7 @@ void LayerTreeHost::ToProtobufForCommit(
 
   // layers_that_should_push_properties_ should be serialized before layer
   // properties because it is cleared during the properties serialization.
-  for (auto layer : layers_that_should_push_properties_)
-    proto->add_layers_that_should_push_properties(layer->id());
+  layer_tree_.ToProtobuf(proto->mutable_layer_tree());
 
   LayerProtoConverter::SerializeLayerProperties(this,
                                                 proto->mutable_layer_updates());
@@ -1621,8 +1623,7 @@ void LayerTreeHost::FromProtobufForCommit(const proto::LayerTreeHost& proto) {
     root_layer_ = new_root_layer;
   }
 
-  for (auto layer_id : proto.layers_that_should_push_properties())
-    layers_that_should_push_properties_.insert(layer_id_map_[layer_id]);
+  layer_tree_.FromProtobuf(proto.layer_tree(), &layer_id_map_);
 
   // Ensure ClientPictureCache contains all the necessary SkPictures before
   // deserializing the properties.