Add a command-line flag to set GPU rasterization multisampling.

content/renderer/render_thread_impl.h

 // 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.
 
 #ifndef CONTENT_RENDERER_RENDER_THREAD_IMPL_H_
 #define CONTENT_RENDERER_RENDER_THREAD_IMPL_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 166 matching lines @@
 #if defined(OS_WIN)
   virtual void PreCacheFont(const LOGFONT& log_font) override;
   virtual void ReleaseCachedFonts() override;
 #endif
   ServiceRegistry* GetServiceRegistry() override;
 
   // CompositorDependencies implementation.
   bool IsImplSidePaintingEnabled() override;
   bool IsGpuRasterizationForced() override;
   bool IsGpuRasterizationEnabled() override;
+  int GpuRasterizationMSAASampleCount() override;
   bool IsLcdTextEnabled() override;
   bool IsDistanceFieldTextEnabled() override;
   bool IsZeroCopyEnabled() override;
   bool IsOneCopyEnabled() override;
   bool IsElasticOverscrollEnabled() override;
   uint32 GetImageTextureTarget() override;
   scoped_refptr<base::SingleThreadTaskRunner>
   GetCompositorMainThreadTaskRunner() override;
   scoped_refptr<base::SingleThreadTaskRunner>
   GetCompositorImplThreadTaskRunner() override;
@@ skipping 385 matching lines @@
   scoped_ptr<MemoryObserver> memory_observer_;
 
   scoped_refptr<base::SingleThreadTaskRunner>
       main_thread_compositor_task_runner_;
 
   scoped_refptr<ResourceSchedulingFilter> resource_scheduling_filter_;
 
   // Compositor settings.
   bool is_gpu_rasterization_enabled_;
   bool is_gpu_rasterization_forced_;
+  int gpu_rasterization_msaa_sample_count_;
   bool is_impl_side_painting_enabled_;
   bool is_lcd_text_enabled_;
   bool is_distance_field_text_enabled_;
   bool is_zero_copy_enabled_;
   bool is_one_copy_enabled_;
   bool is_elastic_overscroll_enabled_;
   unsigned use_image_texture_target_;
 
   std::map<int, mojo::MessagePipeHandle> pending_render_frame_connects_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderThreadImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_THREAD_IMPL_H_