Remove unused variable OcclusionTracker::prevent_occlusion.

cc/trees/layer_tree_host_impl.cc

 // Copyright 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.
 
 #include "cc/trees/layer_tree_host_impl.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/basictypes.h"
@@ skipping 731 matching lines @@
   // texture suddenly appearing in the future.
   bool draw_frame = true;
   // When we have a copy request for a layer, we need to draw no matter
   // what, as the layer may disappear after this frame.
   bool have_copy_request = false;
 
   int layers_drawn = 0;
 
   const DrawMode draw_mode = GetDrawMode(output_surface_.get());
 
-  const bool prevent_occlusion = false;
   LayerIteratorType end =
       LayerIteratorType::End(frame->render_surface_layer_list);
   for (LayerIteratorType it =
            LayerIteratorType::Begin(frame->render_surface_layer_list);
        it != end;
        ++it) {
     RenderPass::Id target_render_pass_id =
         it.target_render_surface_layer()->render_surface()->RenderPassId();
     RenderPass* target_render_pass =
         frame->render_passes_by_id[target_render_pass_id];
 
-    occlusion_tracker.EnterLayer(it, prevent_occlusion);
+    occlusion_tracker.EnterLayer(it);
 
     AppendQuadsData append_quads_data(target_render_pass_id);
 
     if (it.represents_target_render_surface()) {
       if (it->HasCopyRequest()) {
         have_copy_request = true;
         it->TakeCopyRequestsAndTransformToTarget(
             &target_render_pass->copy_requests);
       }
     } else if (it.represents_contributing_render_surface() &&
@@ skipping 2068 matching lines @@
   if (evicted_ui_resources_.empty())
     client_->OnCanDrawStateChanged(CanDraw());
 }
 
 void LayerTreeHostImpl::ScheduleMicroBenchmark(
     scoped_ptr<MicroBenchmarkImpl> benchmark) {
   micro_benchmark_controller_.ScheduleRun(benchmark.Pass());
 }
 
 }  // namespace cc