Implement GLHelperReadbackSupport for GLHelper usage.

content/content_common.gypi

 # 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.
 
 {
   'dependencies': [
     '../base/base.gyp:base',
     '../components/tracing.gyp:tracing',
     '../net/net.gyp:net',
     '../skia/skia.gyp:skia',
@@ skipping 171 matching lines @@
     'common/gamepad_messages.h',
     'common/gamepad_user_gesture.cc',
     'common/gamepad_user_gesture.h',
     'common/geolocation_messages.h',
     'common/gpu/client/command_buffer_proxy_impl.cc',
     'common/gpu/client/command_buffer_proxy_impl.h',
     'common/gpu/client/context_provider_command_buffer.cc',
     'common/gpu/client/context_provider_command_buffer.h',
     'common/gpu/client/gl_helper.cc',
     'common/gpu/client/gl_helper.h',
+    'common/gpu/client/gl_helper_readback_support.cc',
+    'common/gpu/client/gl_helper_readback_support.h',
     'common/gpu/client/gl_helper_scaling.cc',
     'common/gpu/client/gl_helper_scaling.h',
     'common/gpu/client/gpu_channel_host.cc',
     'common/gpu/client/gpu_channel_host.h',
     'common/gpu/client/gpu_memory_buffer_impl.cc',
     'common/gpu/client/gpu_memory_buffer_impl.h',
     'common/gpu/client/gpu_memory_buffer_impl_android.cc',
     'common/gpu/client/gpu_memory_buffer_impl_linux.cc',
     'common/gpu/client/gpu_memory_buffer_impl_mac.cc',
     'common/gpu/client/gpu_memory_buffer_impl_shm.cc',
@@ skipping 446 matching lines @@
         'common/sandbox_linux/bpf_renderer_policy_linux.cc',
         'common/sandbox_linux/bpf_renderer_policy_linux.h',
         'common/sandbox_linux/sandbox_bpf_base_policy_linux.cc',
         'common/sandbox_linux/sandbox_bpf_base_policy_linux.h',
       ],
     }, {
       'defines': ['USE_SECCOMP_BPF'],
     }],
   ],
 }