cc: Force update tile priorities for pending tree tiling set on commit.

cc/tiles/picture_layer_tiling_set.cc

Index: cc/tiles/picture_layer_tiling_set.cc
diff --git a/cc/tiles/picture_layer_tiling_set.cc b/cc/tiles/picture_layer_tiling_set.cc
index 477124b2a49477fc98dbf36240d4213037fbe326..34f3fa23b89236aa997d24364cdf8fec535483aa 100644
--- a/cc/tiles/picture_layer_tiling_set.cc
+++ b/cc/tiles/picture_layer_tiling_set.cc
@@ -160,13 +160,13 @@ void PictureLayerTilingSet::UpdateTilingsToCurrentRasterSourceForCommit(
   for (const std::unique_ptr<PictureLayerTiling>& tiling : tilings_) {
     DCHECK(tree_ != PENDING_TREE || !tiling->has_tiles());
     tiling->SetRasterSourceAndResize(raster_source);
-
-    // We can commit on either active or pending trees, but only active one can
-    // have tiles at this point.
-    if (tree_ == ACTIVE_TREE) {
-      tiling->Invalidate(layer_invalidation);
-      state_since_last_tile_priority_update_.invalidated = true;
-    }
+    tiling->Invalidate(layer_invalidation);

[vmpstr, 2016/11/23 02:08:52]

Can you leave invalidate in the is active tree case only? Otherwise, it will do
extra unnecessary work. 

[sunnyps, 2016/11/23 02:16:07]

Done.

+    // Force |UpdateTilePriorities| on commit for cases where the compositor is
+    // heavily pipelined resulting in back to back draw and commit. This
+    // prevents the early out from |UpdateTilePriorities| because frame time
+    // didn't change. That in turn causes an early out from PrepareTiles which
+    // can cause checkerboarding.
+    state_since_last_tile_priority_update_.invalidated = true;
 
     // This is needed for cases where the live tiles rect didn't change but
     // recordings exist in the raster source that did not exist on the last