Add command buffer support for GL_RGB CHROMIUM image emulation.

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 <stdint.h>
 
 #include <string>
@@ skipping 56 matching lines @@
                                     gfx::OverlayTransform transform,
                                     const gfx::Rect& bounds_rect,
                                     const gfx::RectF& crop_rect) = 0;
 
   // Dumps information about the memory backing the GLImage to a dump named
   // |dump_name|.
   virtual void OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd,
                             uint64_t process_tracing_id,
                             const std::string& dump_name) = 0;
 
+  // If this returns true, then the command buffer client has requested a
+  // CHROMIUM image with internalformat GL_RGB, but the platform only supports
+  // GL_RGBA. The client is responsible for implementing appropriate
+  // workarounds. The only support that the command buffer provides is format
+  // validation during calls to copyTexImage2D and copySubTexImage2D.
+  //
+  // This is a workaround that is not intended to become a permanent part of the
+  // GLImage API. Theoretically, when Apple fixes their drivers, this can be
+  // removed. https://crbug.com/581777#c36
+  virtual bool EmulatingRGB() const;
+
  protected:
   virtual ~GLImage() {}
 
  private:
   friend class base::RefCounted<GLImage>;
 
   DISALLOW_COPY_AND_ASSIGN(GLImage);
 };
 
 }  // namespace gl
 
 #endif  // UI_GL_GL_IMAGE_H_