Add support for EXT_image_flush_external extension

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 50 matching lines @@
                                const gfx::Point& offset,
                                const gfx::Rect& rect) = 0;
 
   // Schedule image as an overlay plane to be shown at swap time for |widget|.
   virtual bool ScheduleOverlayPlane(gfx::AcceleratedWidget widget,
                                     int z_order,
                                     gfx::OverlayTransform transform,
                                     const gfx::Rect& bounds_rect,
                                     const gfx::RectF& crop_rect) = 0;
 
+  // Flush any preceding rendering for the image.
+  virtual void Flush() = 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
@@ skipping 16 matching lines @@
 
  private:
   friend class base::RefCounted<GLImage>;
 
   DISALLOW_COPY_AND_ASSIGN(GLImage);
 };
 
 }  // namespace gl
 
 #endif  // UI_GL_GL_IMAGE_H_