ui: Add gfx::BufferUsage::SCANOUT_CPU_READ_WRITE.

ui/gfx/mojo/buffer_types.mojom

 // Copyright 2016 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.
 
 module gfx.mojom;
 
 // gfx::BufferFormat
 enum BufferFormat {
   ATC,
   ATCIA,
@@ skipping 12 matching lines @@
   YUV_420_BIPLANAR,
   UYVY_422,
 
   LAST = UYVY_422
 };
 
 // gfx::BufferUsage
 enum BufferUsage {
   GPU_READ,
   SCANOUT,
+  SCANOUT_CPU_READ_WRITE,
   GPU_READ_CPU_READ_WRITE,
   GPU_READ_CPU_READ_WRITE_PERSISTENT,
 
   LAST = GPU_READ_CPU_READ_WRITE_PERSISTENT
 };
 
 // gfx::GpuMemoryBufferType
 enum GpuMemoryBufferType {
   EMPTY_BUFFER,
   SHARED_MEMORY_BUFFER,
@@ skipping 26 matching lines @@
 // gfx::GpuMemoryBufferHandle
 struct GpuMemoryBufferHandle {
   GpuMemoryBufferType type;
   GpuMemoryBufferId id;
   handle? shared_memory_handle;
   uint32 offset;
   uint32 stride;
   NativePixmapHandle? native_pixmap_handle;
   handle? mach_port;
 };