cc: Mirror LiveTilesRect and tiles between active and recycled trees.

cc/resources/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/resources/picture_layer_tiling_set.h"
 
 #include <limits>
 #include <set>
 #include <vector>
 
@@ skipping 72 matching lines @@
 
   // For unshared tilings, invalidate tiles and update them to the new raster
   // source.
   for (PictureLayerTiling* tiling : tilings_) {
     if (twin_set && twin_set->FindTilingWithScale(tiling->contents_scale()))
       continue;
 
     tiling->Resize(layer_bounds);
     tiling->Invalidate(layer_invalidation);
     tiling->SetRasterSource(raster_source);
-    // TODO(danakj): Is this needed anymore? Won't they already exist?
+    // 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();
 
     // If |twin_set| is present, use the resolutions from there. Otherwise leave
     // all resolutions as they are.
     if (twin_set)
       tiling->set_resolution(NON_IDEAL_RESOLUTION);
   }
 
   tilings_.sort(LargestToSmallestScaleFunctor());
 
@@ skipping 495 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