Ensure Layers have valid sequence numbers for PropertyTrees

cc/trees/layer_tree_host_unittest_serialization.cc

 // Copyright 2015 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 "cc/layers/heads_up_display_layer.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/layer_settings.h"
 #include "cc/proto/layer.pb.h"
@@ skipping 124 matching lines @@
       EXPECT_EQ(nullptr, layer_tree_host_dst_->outer_viewport_scroll_layer_);
     }
     EXPECT_EQ(layer_tree_host_src_->selection_,
               layer_tree_host_dst_->selection_);
     EXPECT_EQ(layer_tree_host_src_->property_trees_,
               layer_tree_host_dst_->property_trees_);
     EXPECT_EQ(layer_tree_host_src_->surface_id_namespace_,
               layer_tree_host_dst_->surface_id_namespace_);
     EXPECT_EQ(layer_tree_host_src_->next_surface_sequence_,
               layer_tree_host_dst_->next_surface_sequence_);
+
+    // All layers must have a property tree index that matches PropertyTrees.
+    if (layer_tree_host_dst_->property_trees_.sequence_number) {
+      int seq_num = layer_tree_host_dst_->property_trees_.sequence_number;
+      LayerTreeHostCommon::CallFunctionForSubtree(
+          layer_tree_host_dst_->root_layer_.get(), [seq_num](Layer* layer) {
+            EXPECT_EQ(seq_num, layer->property_tree_sequence_number());
+          });
+    }
   }
 
   void RunAllMembersChangedTest() {
     layer_tree_host_src_->needs_full_tree_sync_ =
         !layer_tree_host_src_->needs_full_tree_sync_;
     layer_tree_host_src_->needs_meta_info_recomputation_ =
         !layer_tree_host_src_->needs_meta_info_recomputation_;
     layer_tree_host_src_->source_frame_number_ *= 3;
     layer_tree_host_src_->meta_information_sequence_number_ *= 3;
 
@@ skipping 149 matching lines @@
 
 TEST_F(LayerTreeHostSerializationTest, LayersChanged) {
   RunLayersChangedTest();
 }
 
 TEST_F(LayerTreeHostSerializationTest, LayersChangedMultipleSerializations) {
   LayersChangedMultipleSerializations();
 }
 
 }  // namespace cc