Remove unused variable OcclusionTracker::prevent_occlusion.

cc/trees/occlusion_tracker.h

 // Copyright 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 CC_TREES_OCCLUSION_TRACKER_H_
 #define CC_TREES_OCCLUSION_TRACKER_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 19 matching lines @@
 // once finished with the layer, occlusion behind the layer should be marked by
 // calling MarkOccludedBehindLayer().
 template <typename LayerType, typename RenderSurfaceType>
 class CC_EXPORT OcclusionTrackerBase {
  public:
   OcclusionTrackerBase(gfx::Rect screen_space_clip_rect,
                        bool record_metrics_for_frame);
   ~OcclusionTrackerBase();
 
   // Called at the beginning of each step in the LayerIterator's front-to-back
-  // traversal. If |prevent_occlusion| is true, the layer will be considered
-  // unoccluded.
-  void EnterLayer(const LayerIteratorPosition<LayerType>& layer_iterator,
-                  bool prevent_occlusion);
+  // traversal.
+  void EnterLayer(const LayerIteratorPosition<LayerType>& layer_iterator);
   // Called at the end of each step in the LayerIterator's front-to-back
   // traversal.
   void LeaveLayer(const LayerIteratorPosition<LayerType>& layer_iterator);
 
   // Returns true if the given rect in content space for a layer is fully
   // occluded in either screen space or the layer's target surface.
   // |render_target| is the contributing layer's render target, and
   // |draw_transform| and |impl_draw_transform_is_unknown| are relative to that.
   bool Occluded(const LayerType* render_target,
                 gfx::Rect content_rect,
@@ skipping 85 matching lines @@
   // one. We then perform any operations required for merging results from the
   // child subtree into its parent.
   void LeaveToRenderTarget(const LayerType* new_target);
 
   // Add the layer's occlusion to the tracked state.
   void MarkOccludedBehindLayer(const LayerType* layer);
 
   gfx::Rect screen_space_clip_rect_;
   scoped_ptr<class OverdrawMetrics> overdraw_metrics_;
   gfx::Size minimum_tracking_size_;
-  bool prevent_occlusion_;
 
   // This is used for visualizing the occlusion tracking process.
   std::vector<gfx::Rect>* occluding_screen_space_rects_;
   std::vector<gfx::Rect>* non_occluding_screen_space_rects_;
 
   DISALLOW_COPY_AND_ASSIGN(OcclusionTrackerBase);
 };
 
 typedef OcclusionTrackerBase<Layer, RenderSurface> OcclusionTracker;
 typedef OcclusionTrackerBase<LayerImpl, RenderSurfaceImpl> OcclusionTrackerImpl;
 #if !defined(COMPILER_MSVC)
 extern template class OcclusionTrackerBase<Layer, RenderSurface>;
 extern template class OcclusionTrackerBase<LayerImpl, RenderSurfaceImpl>;
 #endif
 
 }  // namespace cc
 
 #endif  // CC_TREES_OCCLUSION_TRACKER_H_