Add gfx::GpuMemoryBuffer::YUV_420 and GpuMemoryBufferImplSharedMemory support

ui/gfx/gpu_memory_buffer.h

 // 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.
 
 #ifndef UI_GFX_GPU_MEMORY_BUFFER_H_
 #define UI_GFX_GPU_MEMORY_BUFFER_H_
 
 #include "base/memory/shared_memory.h"
 #include "build/build_config.h"
 #include "ui/gfx/gfx_export.h"
@@ skipping 33 matching lines @@
   // client's address space.
   enum Format {
     ATC,
     ATCIA,
     DXT1,
     DXT5,
     ETC1,
     RGBA_8888,
     RGBX_8888,
     BGRA_8888,
+    YUV_420,
 
-    FORMAT_LAST = BGRA_8888
+    FORMAT_LAST = YUV_420
   };
 
   // The usage mode affects how a buffer can be used. Only buffers created with
   // MAP can be mapped into the client's address space and accessed by the CPU.
   enum Usage { MAP, SCANOUT, USAGE_LAST = SCANOUT };
 
   virtual ~GpuMemoryBuffer() {}
 
   // Maps each plane of the buffer into the client's address space so it can be
   // written to by the CPU. A pointer to plane K is stored at index K-1 of the
@@ skipping 19 matching lines @@
   // Returns a platform specific handle for this buffer.
   virtual GpuMemoryBufferHandle GetHandle() const = 0;
 
   // Type-checking downcast routine.
   virtual ClientBuffer AsClientBuffer() = 0;
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_GPU_MEMORY_BUFFER_H_