gpu: Add ARB_occlusion_query support.

cc/output/gl_renderer.h

 // Copyright 2010 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 CC_OUTPUT_GL_RENDERER_H_
 #define CC_OUTPUT_GL_RENDERER_H_
 
 #include <deque>
 #include <vector>
 
@@ skipping 346 matching lines @@
   // The method FlippedFramebuffer determines whether the framebuffer associated
   // with a DrawingFrame is flipped. It makes the assumption that the
   // DrawingFrame is being used as part of a render pass. If a DrawingFrame is
   // not being used as part of a render pass, setting it here forces
   // FlippedFramebuffer to return |true|.
   bool force_drawing_frame_framebuffer_unflipped_ = false;
 
   BoundGeometry bound_geometry_;
   ColorLUTCache color_lut_cache_;
 
+  bool use_occlusion_query_;
   unsigned offscreen_stencil_renderbuffer_id_ = 0;
   gfx::Size offscreen_stencil_renderbuffer_size_;
 
   base::WeakPtrFactory<GLRenderer> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(GLRenderer);
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_GL_RENDERER_H_