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

cc/tiles/picture_layer_tiling_set.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/tiles/picture_layer_tiling_set.h"
 
 #include <stddef.h>
 
 #include <limits>
 #include <set>
@@ skipping 142 matching lines @@
     float maximum_contents_scale_key) {
   RemoveTilingsBelowScaleKey(minimum_contents_scale_key);
   RemoveTilingsAboveScaleKey(maximum_contents_scale_key);
 
   raster_source_ = raster_source;
 
   // Invalidate tiles and update them to the new raster source.
   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
     // raster source.
     tiling->CreateMissingTilesInLiveTilesRect();
   }
   VerifyTilings(nullptr /* pending_twin_set */);
 }
 
 void PictureLayerTilingSet::UpdateRasterSourceDueToLCDChange(
@@ skipping 598 matching lines @@
     case LOWER_THAN_LOW_RES:
       range = TilingRange(low_res_range.end, tilings_size);
       break;
   }
 
   DCHECK_LE(range.start, range.end);
   return range;
 }
 
 }  // namespace cc