Track occlusion per tree on Tile.

cc/resources/tile.h

Index: cc/resources/tile.h
diff --git a/cc/resources/tile.h b/cc/resources/tile.h
index 29acf80a1e35d116e309dde63d4a9f3c8d5aa1a3..716ea99024703a4e4e8b0363d8d427201770ff6a 100644
--- a/cc/resources/tile.h
+++ b/cc/resources/tile.h
@@ -128,8 +128,11 @@ class CC_EXPORT Tile : public RefCountedManaged<Tile> {
     return managed_state_.tile_versions[mode];
   }
 
-  void set_is_occluded(bool is_occluded) { is_occluded_ = is_occluded; }
-  bool is_occluded() const { return is_occluded_; }
+  void set_is_occluded(WhichTree tree, bool is_occluded) {
+    is_occluded_[tree] = is_occluded;
+  }
+
+  bool is_occluded(WhichTree tree) const { return is_occluded_[tree]; }
 
  private:
   friend class TileManager;
@@ -160,7 +163,7 @@ class CC_EXPORT Tile : public RefCountedManaged<Tile> {
   gfx::Rect content_rect_;
   float contents_scale_;
   gfx::Rect opaque_rect_;
-  bool is_occluded_;
+  bool is_occluded_[NUM_TREES];
 
   TilePriority priority_[NUM_TREES];
   ManagedTileState managed_state_;