cc: Simplify the logic for deciding to update tile priorities.

cc/picture_layer_impl.cc

Index: cc/picture_layer_impl.cc
diff --git a/cc/picture_layer_impl.cc b/cc/picture_layer_impl.cc
index fc0e9d0952ba72ff45a05da559b6c6cb73c815de..2b94fd2cc5939d11babaa7802d7773b7b5de918b 100644
--- a/cc/picture_layer_impl.cc
+++ b/cc/picture_layer_impl.cc
@@ -216,10 +216,22 @@ void PictureLayerImpl::dumpLayerProperties(std::string*, int indent) const {
 }
 
 void PictureLayerImpl::updateTilePriorities() {
+  if (!tilings_->num_tilings())
+    return;
+
   int current_source_frame_number = layerTreeImpl()->source_frame_number();
   double current_frame_time =
       (layerTreeImpl()->CurrentFrameTime() - base::TimeTicks()).InSecondsF();
 
+  bool has_tiling_that_needs_update = false;
+  for (size_t i = 0; i < tilings_->num_tilings(); ++i) {
+    if (tilings_->tiling_at(i)->needs_update_tile_priorities(
+            current_source_frame_number, current_frame_time))
+      has_tiling_that_needs_update = true;
+  }
+  if (!has_tiling_that_needs_update)
+    return;
+
   gfx::Transform current_screen_space_transform =
       screenSpaceTransform();
 
@@ -504,6 +516,7 @@ PictureLayerTiling* PictureLayerImpl::AddTiling(float contents_scale) {
   DCHECK(contents_scale >= layerTreeImpl()->settings().minimumContentsScale);
 
   PictureLayerTiling* tiling = tilings_->AddTiling(contents_scale);
+  layerTreeImpl()->set_needs_update_tile_priorities();
 
   const Region& recorded = pile_->recorded_region();
   DCHECK(!recorded.IsEmpty());