Add underlays and split off common overlay functionality

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 280 matching lines @@
         'output/managed_memory_policy.cc',
         'output/managed_memory_policy.h',
         'output/output_surface.cc',
         'output/output_surface.h',
         'output/output_surface_client.h',
         'output/overlay_candidate.cc',
         'output/overlay_candidate.h',
         'output/overlay_candidate_validator.h',
         'output/overlay_processor.cc',
         'output/overlay_processor.h',
+        'output/overlay_strategy_common.cc',
+        'output/overlay_strategy_common.h',
         'output/overlay_strategy_single_on_top.cc',
         'output/overlay_strategy_single_on_top.h',
+        'output/overlay_strategy_underlay.cc',
+        'output/overlay_strategy_underlay.h',
         'output/program_binding.cc',
         'output/program_binding.h',
         'output/render_surface_filters.cc',
         'output/render_surface_filters.h',
         'output/renderer.cc',
         'output/renderer.h',
         'output/renderer_capabilities.cc',
         'output/renderer_capabilities.h',
         'output/renderer_settings.cc',
         'output/renderer_settings.h',
@@ skipping 302 matching lines @@
         'surfaces/surface_resource_holder.cc',
         'surfaces/surface_resource_holder.h',
         'surfaces/surfaces_export.h',
       ],
       'includes': [
         '../build/android/increase_size_for_speed.gypi',
       ],
     },
   ],
 }