cc: Update picture pile on tiles to prevent memory leak

cc/picture_layer_tiling.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/picture_layer_tiling.h"
 
 #include "cc/math_util.h"
 #include "ui/gfx/rect_conversions.h"
 #include "ui/gfx/size_conversions.h"
 
@@ skipping 297 matching lines @@
     priority.time_to_visible_in_seconds =
         TilePriority::TimeForBoundsToIntersect(
             last_screen_rect, current_screen_rect, time_delta, view_rect);
 
     priority.distance_to_visible_in_pixels =
         TilePriority::manhattanDistance(current_screen_rect, view_rect);
     it->second->set_priority(tree, priority);
   }
 }
 
-void PictureLayerTiling::MoveTilePriorities(WhichTree src_tree,
-                                            WhichTree dst_tree) {
-  DCHECK(src_tree != dst_tree);
+void PictureLayerTiling::DidBecomeActive() {
   for (TileMap::const_iterator it = tiles_.begin(); it != tiles_.end(); ++it) {
-    it->second->set_priority(dst_tree, it->second->priority(src_tree));
-    it->second->set_priority(src_tree, TilePriority());
+    it->second->set_priority(ACTIVE_TREE, it->second->priority(PENDING_TREE));
+    it->second->set_priority(PENDING_TREE, TilePriority());
+
+    // Tile holds a ref onto a picture pile. If the tile never gets invalidated
+    // and recreated, then that picture pile ref could exist indefinitely.  To
+    // prevent this, ask the client to update the pile to its own ref.  This
+    // will cause PicturePileImpls and their clones to get deleted once the
+    // corresponding PictureLayerImpl and any in flight raster jobs go out of
+    // scope.
+    client_->UpdatePile(it->second);
   }
 }
 
 }  // namespace cc