Ensure Layers have valid sequence numbers for PropertyTrees

cc/trees/layer_tree_host.cc

 // Copyright 2011 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/trees/layer_tree_host.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 1417 matching lines @@
   outer_viewport_scroll_layer_ =
       UpdateAndGetLayer(outer_viewport_scroll_layer_.get(),
                         proto.outer_viewport_scroll_layer_id(), layer_id_map_);
 
   LayerSelectionFromProtobuf(&selection_, proto.selection());
 
   // It is required to create new PropertyTrees before deserializing it.
   property_trees_ = PropertyTrees();
   property_trees_.FromProtobuf(proto.property_trees());
 
+  // Forcefully override the sequence number of all layers in the tree to have
+  // a valid sequence number. Changing the sequence number for a layer does not
+  // need a commit, so the value will become out of date for layers that are not
+  // updated for other reasons. All layers that at this point are part of the
+  // layer tree are valid, so it is OK that they have a valid sequence number.
+  int seq_num = property_trees_.sequence_number;
+  LayerTreeHostCommon::CallFunctionForSubtree(
+      root_layer(), [seq_num](Layer* layer) {
+        layer->set_property_tree_sequence_number(seq_num);
+      });
+
   surface_id_namespace_ = proto.surface_id_namespace();
   next_surface_sequence_ = proto.next_surface_sequence();
 }
 
 }  // namespace cc