Use MSAA in GPU rasterization if Skia suggests it

cc/output/output_surface.cc

 // Copyright (c) 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 "cc/output/output_surface.h"
 
 #include <algorithm>
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 358 matching lines @@
         size.width(), size.height(), scale_factor);
   }
   if (software_device_)
     software_device_->Resize(size);
 }
 
 gfx::Size OutputSurface::SurfaceSize() const {
   return surface_size_;
 }
 
+float OutputSurface::SurfaceScaleFactor() const { return device_scale_factor_; }
+
 void OutputSurface::BindFramebuffer() {
   DCHECK(context_provider_);
   context_provider_->ContextGL()->BindFramebuffer(GL_FRAMEBUFFER, 0);
 }
 
 void OutputSurface::SwapBuffers(CompositorFrame* frame) {
   if (frame->software_frame_data) {
     PostSwapBuffersComplete();
     DidSwapBuffers();
     return;
@@ skipping 97 matching lines @@
   TRACE_EVENT1("cc", "OutputSurface::SetMemoryPolicy",
                "bytes_limit_when_visible", policy.bytes_limit_when_visible);
   // Just ignore the memory manager when it says to set the limit to zero
   // bytes. This will happen when the memory manager thinks that the renderer
   // is not visible (which the renderer knows better).
   if (policy.bytes_limit_when_visible)
     client_->SetMemoryPolicy(policy);
 }
 
 }  // namespace cc