cc: Add threaded GPU rasterization.

content/browser/android/in_process/synchronous_compositor_impl.cc

 // Copyright 2013 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.
 
 #include "content/browser/android/in_process/synchronous_compositor_impl.h"
 
 #include "base/auto_reset.h"
 #include "base/bind.h"
 #include "base/lazy_instance.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 136 matching lines @@
   compositor_client_ = nullptr;
 }
 
 bool SynchronousCompositorImpl::InitializeHwDraw() {
   DCHECK(CalledOnValidThread());
   DCHECK(output_surface_);
 
   scoped_refptr<cc::ContextProvider> onscreen_context =
       g_factory.Get().CreateOnscreenContextProviderForCompositorThread();
 
-  bool success = output_surface_->InitializeHwDraw(onscreen_context);
+  scoped_refptr<cc::ContextProvider> worker_context =
+      g_factory.Get().CreateOnscreenContextProviderForCompositorThread();

[boliu, 2015/02/13 18:04:05]

Is it possible/safe to key this off of a command line switch? For webview,
creating and destroying context happens as normal part of operation, not just on
start up/tear down/error. Creating a context is pretty expensive, so it could
have perf impact.

Also just rename the method to CreateContextProviderForCompositor.

[vmiura, 2015/02/13 19:52:34]

We need it whenever GPU rasterization is enabled.  Is it safe to check something
like Content::IsGpuRasterizationEnabled() here?.
Done.

[boliu, 2015/02/13 20:25:52]

Oh I thought the new context will only be used with
--enable-threaded-gpu-rasterization. If it's needed for ganesh in general, then
I don't think it's worth it.

I think the answer to IsGpuRasterizationEnabled is yes. It is safe since it's
just reading a bunch of command line switches.

+
+  bool success =
+      output_surface_->InitializeHwDraw(onscreen_context, worker_context);
 
   if (success)
     g_factory.Get().CompositorInitializedHardwareDraw();
   return success;
 }
 
 void SynchronousCompositorImpl::ReleaseHwDraw() {
   DCHECK(CalledOnValidThread());
   DCHECK(output_surface_);
   output_surface_->ReleaseHwDraw();
@@ skipping 196 matching lines @@
     g_factory.Get();  // Ensure it's initialized.
     SynchronousCompositorImpl::CreateForWebContents(contents);
   }
   SynchronousCompositorImpl* instance =
       SynchronousCompositorImpl::FromWebContents(contents);
   DCHECK(instance);
   instance->SetClient(client);
 }
 
 }  // namespace content