Add support for (de)serializing LayerTreeHost.

cc/cc.gyp

 # Copyright (c) 2012 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
@@ skipping 591 matching lines @@
       # GN version: "//cc/proto"
       'target_name': 'cc_proto',
       'type': '<(component)',
       'sources': [
         'proto/compositor_message.proto',
         'proto/display_item.proto',
         'proto/display_list_recording_source.proto',
         'proto/layer.proto',
         'proto/layer_position_constraint.proto',
         'proto/layer_tree_debug_state.proto',
+        'proto/layer_tree_host.proto',
         'proto/layer_tree_settings.proto',
         'proto/layer_selection_bound.proto',
         'proto/managed_memory_policy.proto',
         'proto/memory_allocation.proto',
         'proto/point.proto',
         'proto/point3f.proto',
         'proto/pointf.proto',
         'proto/property_tree.proto',
         'proto/rect.proto',
         'proto/rectf.proto',
@@ skipping 66 matching lines @@
         'surfaces/surface_resource_holder.cc',
         'surfaces/surface_resource_holder.h',
         'surfaces/surfaces_export.h',
       ],
       'includes': [
         '../build/android/increase_size_for_speed.gypi',
       ],
     },
   ],
 }