cc: Consider visible rect for update tile priority early out.

cc/resources/picture_layer_tiling.h

Index: cc/resources/picture_layer_tiling.h
diff --git a/cc/resources/picture_layer_tiling.h b/cc/resources/picture_layer_tiling.h
index 104ca107753e3ef12fb34f6fca6361d18231309d..a5b1a999346f876f1e743bf6032ee2396b352edf 100644
--- a/cc/resources/picture_layer_tiling.h
+++ b/cc/resources/picture_layer_tiling.h
@@ -254,8 +254,11 @@ class CC_EXPORT PictureLayerTiling {
   // while DidBecomeActive promotes pending priority on a similar set of tiles.
   void DidBecomeRecycled();
 
-  bool NeedsUpdateForFrameAtTime(double frame_time_in_seconds) {
-    return frame_time_in_seconds != last_impl_frame_time_in_seconds_;
+  bool NeedsUpdateForFrameAtTimeAndViewport(
+      double frame_time_in_seconds,
+      const gfx::Rect& viewport_in_layer_space) {
+    return frame_time_in_seconds != last_impl_frame_time_in_seconds_ ||
+           viewport_in_layer_space != last_viewport_in_layer_space_;
   }
 
   void GetAllTilesForTracing(std::set<const Tile*>* tiles) const;
@@ -329,6 +332,7 @@ class CC_EXPORT PictureLayerTiling {
 
   // State saved for computing velocities based upon finite differences.
   double last_impl_frame_time_in_seconds_;
+  gfx::Rect last_viewport_in_layer_space_;
   gfx::Rect last_visible_rect_in_content_space_;
 
   // Iteration rects in content space