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

cc/trees/layer_tree_impl.cc

Index: cc/trees/layer_tree_impl.cc
diff --git a/cc/trees/layer_tree_impl.cc b/cc/trees/layer_tree_impl.cc
index 797d2d138fffa548cba3f8a8433c17d306324911..1b0f2b01d70d8bed01d6b641019c080b3bf611b1 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -505,8 +505,13 @@ bool LayerTreeImpl::UpdateDrawProperties() {
         occlusion_tracker->EnterLayer(it);
 
       LayerImpl* layer = *it;
+      const Occlusion& occlusion_in_layer_space =

[danakj, 2014/09/09 22:11:59]

I think you probably mean in_content_space which is the same thing as layer
space for picture layer now. Cuz it's based on the draw_transform() which comes
from content space.

[vmpstr, 2014/09/10 00:32:24]

Changed. So, it is technically layer space right? It's just called content
space? Note that I've changed this to in_content_space in PLI as well. However,
in PLT it's referred to as layer space, since its content space is different. Am
I understanding the names correctly?

+          occlusion_tracker ? occlusion_tracker->GetCurrentOcclusionForLayer(
+                                  layer->draw_transform())
+                            : Occlusion();
+
       if (it.represents_itself())
-        layer->UpdateTiles(occlusion_tracker.get());
+        layer->UpdateTiles(occlusion_in_layer_space);
 
       if (!it.represents_contributing_render_surface()) {
         if (occlusion_tracker)
@@ -515,10 +520,10 @@ bool LayerTreeImpl::UpdateDrawProperties() {
       }
 
       if (layer->mask_layer())
-        layer->mask_layer()->UpdateTiles(occlusion_tracker.get());
+        layer->mask_layer()->UpdateTiles(occlusion_in_layer_space);
       if (layer->replica_layer() && layer->replica_layer()->mask_layer())
         layer->replica_layer()->mask_layer()->UpdateTiles(
-            occlusion_tracker.get());
+            occlusion_in_layer_space);
 
       if (occlusion_tracker)
         occlusion_tracker->LeaveLayer(it);