compositor: Add rAF-like functionality for the UI.

ui/compositor/compositor.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': [
     {
       'target_name': 'compositor',
       'type': '<(component)',
       'dependencies': [
         '<(DEPTH)/base/base.gyp:base',
         '<(DEPTH)/base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations',
         '<(DEPTH)/cc/cc.gyp:cc',
         '<(DEPTH)/gpu/gpu.gyp:command_buffer_common',
         '<(DEPTH)/skia/skia.gyp:skia',
         '<(DEPTH)/ui/gfx/gfx.gyp:gfx',
         '<(DEPTH)/ui/gfx/gfx.gyp:gfx_geometry',
         '<(DEPTH)/ui/gl/gl.gyp:gl',
       ],
       'defines': [
         'COMPOSITOR_IMPLEMENTATION',
       ],
       'sources': [
         'compositor.cc',
         'compositor.h',
+        'compositor_animation_observer.h',
         'compositor_export.h',
         'compositor_observer.h',
         'compositor_vsync_manager.cc',
         'compositor_vsync_manager.h',
         'compositor_switches.cc',
         'compositor_switches.h',
         'debug_utils.cc',
         'debug_utils.h',
         'dip_util.cc',
         'dip_util.h',
@@ skipping 129 matching lines @@
               'dependencies': [
                 '<(DEPTH)/base/allocator/allocator.gyp:allocator',
               ],
             }],
           ],
         }],
       ],
     },
   ],
 }