cc: Stop passing the occlusion explicitly to UpdateTiles.

cc/trees/layer_tree_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_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <set>
 
@@ skipping 636 matching lines @@
         occlusion_tracker.ComputeVisibleRegionInScreen();
   }
 
   {
     TRACE_EVENT_BEGIN2("cc", "LayerTreeImpl::UpdateDrawProperties::UpdateTiles",
                        "IsActive", IsActiveTree(), "SourceFrameNumber",
                        source_frame_number_);
     const bool resourceless_software_draw =
         (layer_tree_host_impl_->GetDrawMode() ==
          DRAW_MODE_RESOURCELESS_SOFTWARE);
-    static const Occlusion kEmptyOcclusion;
     size_t layers_updated_count = 0;
     bool tile_priorities_updated = false;
     for (PictureLayerImpl* layer : picture_layers_) {
       // TODO(danakj): Remove this to fix crbug.com/446751
       if (!layer->IsDrawnRenderSurfaceLayerListMember())
         continue;
       ++layers_updated_count;
-      const Occlusion& occlusion =
-          settings().use_occlusion_for_tile_prioritization
-              ? layer->draw_properties().occlusion_in_content_space
-              : kEmptyOcclusion;
-      tile_priorities_updated |=
-          layer->UpdateTiles(occlusion, resourceless_software_draw);
+      tile_priorities_updated |= layer->UpdateTiles(resourceless_software_draw);
     }
 
     if (tile_priorities_updated)
       DidModifyTilePriorities();
 
     TRACE_EVENT_END1("cc", "LayerTreeImpl::UpdateTilePriorities",
                      "layers_updated_count", layers_updated_count);
   }
 
   DCHECK(!needs_update_draw_properties_) <<
@@ skipping 947 matching lines @@
     scoped_ptr<PendingPageScaleAnimation> pending_animation) {
   pending_page_scale_animation_ = pending_animation.Pass();
 }
 
 scoped_ptr<PendingPageScaleAnimation>
     LayerTreeImpl::TakePendingPageScaleAnimation() {
   return pending_page_scale_animation_.Pass();
 }
 
 }  // namespace cc