Make ui::Snapshot asynchronous on Android, remove CompositeAndReadback.

ui/snapshot/snapshot.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': 'snapshot',
       'type': '<(component)',
       'dependencies': [
+        '../../base/base.gyp:base',
         '../../skia/skia.gyp:skia',
-        '../../base/base.gyp:base',
         '../base/ui_base.gyp:ui_base',
         '../gfx/gfx.gyp:gfx',
         '../gfx/gfx.gyp:gfx_geometry',
       ],
       'defines': [
         'SNAPSHOT_IMPLEMENTATION',
       ],
       'sources': [
         'snapshot.h',
         'snapshot_android.cc',
+        'snapshot_async.cc',
+        'snapshot_async.h',
         'snapshot_aura.cc',
         'snapshot_export.h',
         'snapshot_ios.mm',
         'snapshot_mac.mm',
         'snapshot_win.cc',
         'snapshot_win.h',
       ],
       'include_dirs': [
         '..',
       ],
       'conditions': [
+        ['use_aura==1 or OS=="android"', {
+          'dependencies': [
+            '../../cc/cc.gyp:cc',
+            '../../gpu/gpu.gyp:command_buffer_common',
+          ],
+        }],
+        ['use_aura!=1 and OS!="android"', {
+          'sources!': [
+            'snapshot_async.cc',
+            'snapshot_async.h',
+          ],
+        }],
         ['use_aura==1', {
           'dependencies': [
-            '../../cc/cc.gyp:cc',
             '../aura/aura.gyp:aura',
             '../compositor/compositor.gyp:compositor',
           ],
         }],
       ],
     },
     {
       'target_name': 'snapshot_unittests',
       'type': '<(gtest_target_type)',
       'dependencies': [
@@ skipping 44 matching lines @@
             'snapshot',
           ],
           'include_dirs': [
             '../..',
           ],
         },
       ],
     }],
   ],
 }