gpu: Use a VAO as required by the core profile in ClearFramebuffer

gpu/command_buffer/service/gles2_cmd_clear_framebuffer.h

 // Copyright 2014 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 GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_CLEAR_FRAMEBUFFER_H_
 #define GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_CLEAR_FRAMEBUFFER_H_
 
 #include "base/macros.h"
 #include "gpu/command_buffer/service/gl_utils.h"
 #include "gpu/gpu_export.h"
@@ skipping 25 matching lines @@
 
  private:
   void Initialize(const gles2::GLES2Decoder* decoder);
   void Destroy();
 
   // The attributes used during invocation of the extension.
   static const GLuint kVertexPositionAttrib = 0;
 
   bool initialized_;
   GLuint program_;
+  GLuint vao_;
   GLuint depth_handle_;
   GLuint color_handle_;
   GLuint buffer_id_;
 
   DISALLOW_COPY_AND_ASSIGN(ClearFramebufferResourceManager);
 };
 
 }  // namespace gpu.
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_CLEAR_FRAMEBUFFER_H_