implement the logic to set tile priorities based on current matrix

cc/picture_layer_tiling_set.cc

Index: cc/picture_layer_tiling_set.cc
diff --git a/cc/picture_layer_tiling_set.cc b/cc/picture_layer_tiling_set.cc
index 5b49a0345580ea52cca9f39beb36ea484eee3d36..c216c3bf35cabe0634483bcfea7302e31e31781b 100644
--- a/cc/picture_layer_tiling_set.cc
+++ b/cc/picture_layer_tiling_set.cc
@@ -157,4 +157,15 @@ PictureLayerTilingSet::Iterator::operator bool() const {
       region_iter_.has_rect();
 }
 
+void PictureLayerTilingSet::UpdateTilePriorities(
+    const gfx::Size& view_port,
+    const gfx::Transform& last_transform,
+    const gfx::Transform& current_transform,
+    double time_delta) {
+  for (size_t i = 0; i < tilings_.size(); ++i) {
+    tilings_[i]->UpdateTilePriorities(
+        view_port, last_transform, current_transform, time_delta);
+  }
+}
+
 }  // namespace cc