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

cc/proto/layer_tree_host.proto

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 syntax = "proto2";
 
 import "display_item.proto";
 import "layer.proto";
 import "layer_selection_bound.proto";
+import "layer_tree.proto";
 import "layer_tree_debug_state.proto";
 import "property_tree.proto";
 import "size.proto";
 import "vector2df.proto";
 
 package cc.proto;
 
 option optimize_for = LITE_RUNTIME;
 
 message SkPictureData {
@@ skipping 24 matching lines @@
   optional float device_scale_factor = 13;
   optional float painted_device_scale_factor = 14;
   optional float page_scale_factor = 15;
   optional float min_page_scale_factor = 16;
   optional float max_page_scale_factor = 17;
   optional Vector2dF elastic_overscroll = 18;
   optional bool has_gpu_rasterization_trigger = 19;
   optional bool content_is_suitable_for_gpu_rasterization = 20;
   optional uint32 background_color = 21; /* SkColor */
   optional bool has_transparent_background = 22;
-  optional bool in_paint_layer_contents = 23;
-  optional int32 id = 24;
-  optional bool next_commit_forces_redraw = 25;
-  optional int32 overscroll_elasticity_layer_id = 26;
-  optional int32 page_scale_layer_id = 27;
-  optional int32 inner_viewport_scroll_layer_id = 28;
-  optional int32 outer_viewport_scroll_layer_id = 29;
-  optional LayerSelection selection = 30;
-  optional PropertyTrees property_trees = 31;
-  optional uint32 surface_client_id = 32;
-  optional uint32 next_surface_sequence = 33;
-  optional uint32 wheel_event_listener_properties = 34;
-  optional bool have_scroll_event_handlers = 35;
-  optional uint32 touch_start_or_move_event_listener_properties = 36;
-  repeated int32 layers_that_should_push_properties = 37;
-  optional uint32 touch_end_or_cancel_event_listener_properties = 38;
-  optional SkPictures pictures = 39;
+  optional int32 id = 23;
+  optional bool next_commit_forces_redraw = 24;
+  optional int32 overscroll_elasticity_layer_id = 25;
+  optional int32 page_scale_layer_id = 26;
+  optional int32 inner_viewport_scroll_layer_id = 27;
+  optional int32 outer_viewport_scroll_layer_id = 28;
+  optional LayerSelection selection = 29;
+  optional PropertyTrees property_trees = 30;
+  optional uint32 surface_client_id = 31;
+  optional uint32 next_surface_sequence = 32;
+  optional uint32 wheel_event_listener_properties = 33;
+  optional bool have_scroll_event_handlers = 34;
+  optional uint32 touch_start_or_move_event_listener_properties = 35;
+  optional LayerTree layer_tree = 36;
+  optional uint32 touch_end_or_cancel_event_listener_properties = 37;
+  optional SkPictures pictures = 38;
 }