Reland of: cc: Add occlusion checker as a fixed view of occlusion tracker.

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 <limits>
 #include <set>
 
 #include "base/debug/trace_event.h"
@@ skipping 502 matching lines @@
     typedef LayerIterator<LayerImpl> LayerIteratorType;
     LayerIteratorType end = LayerIteratorType::End(&render_surface_layer_list_);
     for (LayerIteratorType it =
              LayerIteratorType::Begin(&render_surface_layer_list_);
          it != end;
          ++it) {
       if (occlusion_tracker)
         occlusion_tracker->EnterLayer(it);
 
       LayerImpl* layer = *it;
+      const Occlusion& occlusion_in_content_space =
+          occlusion_tracker ? occlusion_tracker->GetCurrentOcclusionForLayer(
+                                  layer->draw_transform())
+                            : Occlusion();
+
       if (it.represents_itself())
-        layer->UpdateTiles(occlusion_tracker.get());
+        layer->UpdateTiles(occlusion_in_content_space);
 
       if (!it.represents_contributing_render_surface()) {
         if (occlusion_tracker)
           occlusion_tracker->LeaveLayer(it);
         continue;
       }
 
       if (layer->mask_layer())
-        layer->mask_layer()->UpdateTiles(occlusion_tracker.get());
+        layer->mask_layer()->UpdateTiles(occlusion_in_content_space);
       if (layer->replica_layer() && layer->replica_layer()->mask_layer())
         layer->replica_layer()->mask_layer()->UpdateTiles(
-            occlusion_tracker.get());
+            occlusion_in_content_space);
 
       if (occlusion_tracker)
         occlusion_tracker->LeaveLayer(it);
     }
   }
 
   DCHECK(!needs_update_draw_properties_) <<
       "CalcDrawProperties should not set_needs_update_draw_properties()";
   return true;
 }
@@ skipping 886 matching lines @@
 
 void LayerTreeImpl::InputScrollAnimationFinished() {
   layer_tree_host_impl_->ScrollEnd();
 }
 
 BlockingTaskRunner* LayerTreeImpl::BlockingMainThreadTaskRunner() const {
   return proxy()->blocking_main_thread_task_runner();
 }
 
 }  // namespace cc