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

cc/resources/picture_layer_tiling.cc

Index: cc/resources/picture_layer_tiling.cc
diff --git a/cc/resources/picture_layer_tiling.cc b/cc/resources/picture_layer_tiling.cc
index 736240c976a98f0e6cba2b340e01c72b9e96268b..1dedf5bbf70ec767c1999f5ce21b2c0477ae4001 100644
--- a/cc/resources/picture_layer_tiling.cc
+++ b/cc/resources/picture_layer_tiling.cc
@@ -31,7 +31,7 @@ PictureLayerTiling::PictureLayerTiling(float contents_scale)
       tiling_data_(gfx::Size(), gfx::Size(), true),
       resolution_(NON_IDEAL_RESOLUTION),
       last_source_frame_number_(0),
-      last_impl_frame_time_(0) {
+      last_impl_frame_time_(0.0) {
 }
 
 PictureLayerTiling::~PictureLayerTiling() {
@@ -349,29 +349,12 @@ void PictureLayerTiling::UpdateTilePriorities(
     float current_layer_contents_scale,
     const gfx::Transform& last_screen_transform,
     const gfx::Transform& current_screen_transform,
-    int current_source_frame_number,
     double current_frame_time,
     bool store_screen_space_quads_on_tiles,
     size_t max_tiles_for_interest_area) {
   if (ContentRect().IsEmpty())
     return;
 
-  bool first_update_in_new_source_frame =
-      current_source_frame_number != last_source_frame_number_;
-
-  bool first_update_in_new_impl_frame =
-      current_frame_time != last_impl_frame_time_;
-
-  // In pending tree, this is always called. We update priorities:
-  // - Immediately after a commit (first_update_in_new_source_frame).
-  // - On animation ticks after the first frame in the tree
-  //   (first_update_in_new_impl_frame).
-  // In active tree, this is only called during draw. We update priorities:
-  // - On draw if properties were not already computed by the pending tree
-  //   and activated for the frame (first_update_in_new_impl_frame).
-  if (!first_update_in_new_impl_frame && !first_update_in_new_source_frame)
-    return;
-
   double time_delta = 0;
   if (last_impl_frame_time_ != 0 && last_layer_bounds == current_layer_bounds)
     time_delta = current_frame_time - last_impl_frame_time_;
@@ -506,7 +489,6 @@ void PictureLayerTiling::UpdateTilePriorities(
     }
   }
 
-  last_source_frame_number_ = current_source_frame_number;
   last_impl_frame_time_ = current_frame_time;
 }