gpu: Mailbox emulation with EGLImage

ui/gl/gl_image.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 UI_GL_GL_IMAGE_H_
 #define UI_GL_GL_IMAGE_H_
 
 #include "base/memory/ref_counted.h"
 #include "ui/gfx/gpu_memory_buffer.h"
 #include "ui/gfx/native_widget_types.h"
@@ skipping 21 matching lines @@
 
   // Release image from texture currently bound to |target|.
   virtual void ReleaseTexImage(unsigned target);
 
   // Called before the texture is used for drawing.
   virtual void WillUseTexImage();
 
   // Called after the texture has been used for drawing.
   virtual void DidUseTexImage();
 
+  // Called before the texture image data will be modified.
+  virtual void WillModifyTexImage();
+
+  // Called after the texture image data has been modified.
+  virtual void DidModifyTexImage();

[reveman, 2014/03/12 22:53:02]

while here, do you mind making these and all functions above pure virtual? We
might as well have the compiler tell us when a function is not implemented
instead of default implementations with NOTIMPLEMENTED statements.
SetReleaseAfterUse can have a default implementation as it's a workaround.

+
   // Indicate that image should be released after use.
   // (For an Android work-around only).
   virtual void SetReleaseAfterUse();
 
   // Create a GL image for a window.
   static scoped_refptr<GLImage> CreateGLImage(gfx::PluginWindowHandle window);
 
   // Create a GL image for a GPU Memory buffer.
   static scoped_refptr<GLImage> CreateGLImageForGpuMemoryBuffer(
       gfx::GpuMemoryBufferHandle buffer,
       gfx::Size size,
       unsigned internalformat);
 
  protected:
   virtual ~GLImage();
 
  private:
   friend class base::RefCounted<GLImage>;
 
   DISALLOW_COPY_AND_ASSIGN(GLImage);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GL_GL_IMAGE_H_