Allow GLSurface to indicate that it supports a specific extension.

ui/gfx/gl/gl_surface_egl.h

 // Copyright (c) 2011 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_GL_GL_SURFACE_EGL_H_
 #define UI_GFX_GL_GL_SURFACE_EGL_H_
 #pragma once
 
 #if defined(OS_WIN)
 #include <windows.h>
@@ skipping 45 matching lines @@
   NativeViewGLSurfaceEGL(bool software, gfx::PluginWindowHandle window);
   virtual ~NativeViewGLSurfaceEGL();
 
   // Implement GLSurface.
   virtual bool Initialize();
   virtual void Destroy();
   virtual bool IsOffscreen();
   virtual bool SwapBuffers();
   virtual gfx::Size GetSize();
   virtual EGLSurface GetHandle();
-  virtual bool SupportsPostSubBuffer();
+  virtual std::string GetExtensions();
   virtual bool PostSubBuffer(int x, int y, int width, int height);
 
  private:
   gfx::PluginWindowHandle window_;
   EGLSurface surface_;
   bool supports_post_sub_buffer_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeViewGLSurfaceEGL);
 };
 
@@ skipping 16 matching lines @@
  private:
   gfx::Size size_;
   EGLSurface surface_;
 
   DISALLOW_COPY_AND_ASSIGN(PbufferGLSurfaceEGL);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_GL_GL_SURFACE_EGL_H_