Add a flag for enabling compositor property trees

cc/trees/layer_tree_settings.h

 // 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.
 
 #ifndef CC_TREES_LAYER_TREE_SETTINGS_H_
 #define CC_TREES_LAYER_TREE_SETTINGS_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 63 matching lines @@
   bool use_zero_copy;
   bool use_partial_raster;
   bool enable_elastic_overscroll;
   // An array of image texture targets for each GpuMemoryBuffer format.
   std::vector<unsigned> use_image_texture_targets;
   bool ignore_root_layer_flings;
   size_t scheduled_raster_task_limit;
   bool use_occlusion_for_tile_prioritization;
   bool record_full_layer;
   bool verify_property_trees;
+  bool use_property_trees;
   bool image_decode_tasks_enabled;
   bool use_compositor_animation_timelines;
   bool wait_for_beginframe_interval;
   int max_staging_buffer_usage_in_bytes;
   ManagedMemoryPolicy memory_policy_;
 
   LayerTreeDebugState initial_debug_state;
 
   SchedulerSettings ToSchedulerSettings() const;
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_SETTINGS_H_