The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e1d86515496285e3b5f593fa79d72daec6e64feb

commit e1d86515496285e3b5f593fa79d72daec6e64feb
Author: penghuang <penghuang@chromium.org>
Date: Fri Jul 08 18:15:00 2016

mus+ash: Enable Chrome HW rendering in mus+ash

This change enables the HW supports in mus+ash by
 * Wire up ui service GPU channel.
 * Always create offscreen GL context for gfx::AcceleratedWidget (mus window) in
   browser process.
 * Provide a MusBrowserCompositorOutputSurface.
   In MusBrowserCompositorOutputSurface::SwapBuffers(), we use
   CommandBufferProxyImpl::TakeFrontBuffer() to take the offscreen GL context's
   front buffer into a mailbox, insert a sync token, and send mailbox+sync to
   the ui service process.

Know issue:
 GPUInfo is not sent to renderer, so some webgl demos don't work.

BUG= 622708 
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review-Url: https://codereview.chromium.org/2096843002
Cr-Commit-Position: refs/heads/master@{#404441}

[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/content/browser/BUILD.gn
[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/content/browser/browser_main_loop.cc
[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/content/browser/compositor/DEPS
[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/content/browser/compositor/gpu_process_transport_factory.cc
[add] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/content/browser/compositor/mus_browser_compositor_output_surface.cc
[add] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/content/browser/compositor/mus_browser_compositor_output_surface.h
[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/content/browser/gpu/browser_gpu_channel_host_factory.cc
[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/content/browser/gpu/gpu_data_manager_impl_private.cc
[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/content/browser/gpu/gpu_process_host.cc
[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/content/browser/renderer_host/render_process_host_impl.cc
[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/content/common/gpu/client/context_provider_command_buffer.cc
[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/content/public/common/content_switches.cc
[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/content/public/common/content_switches.h
[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/content/renderer/render_thread_impl.cc
[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/services/ui/common/gpu_service.cc
[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/services/ui/gpu/gpu_service_mus.cc
[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/services/ui/public/cpp/window_surface_client.h
[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/ui/views/mus/native_widget_mus.cc
[modify] https://crrev.com/e1d86515496285e3b5f593fa79d72daec6e64feb/ui/views/mus/window_tree_host_mus.h