cc: Introduce forward_begin_frames_to_children and use_external_begin_frame_source

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 "base/basictypes.h"
 #include "cc/base/cc_export.h"
 #include "cc/debug/layer_tree_debug_state.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/gfx/geometry/size.h"
 
 namespace cc {
 
 class CC_EXPORT LayerTreeSettings {
  public:
   LayerTreeSettings();
   ~LayerTreeSettings();
 
   bool impl_side_painting;
   bool allow_antialiasing;
   bool force_antialiasing;
   bool force_blending_with_shaders;
   bool throttle_frame_production;
   bool single_thread_proxy_scheduler;
-  bool begin_frame_scheduling_enabled;
+  bool use_external_begin_frame_source;
+  bool forward_begin_frames_to_children;
   bool main_frame_before_activation_enabled;
   bool using_synchronous_renderer_compositor;
   bool disable_hi_res_timer_tasks_on_battery;
   bool report_overscroll_only_for_scrollable_axes;
   bool per_tile_painting_enabled;
   bool partial_swap_enabled;
   bool accelerated_animation_enabled;
   bool can_use_lcd_text;
   bool use_distance_field_text;
   bool should_clear_root_render_pass;
@@ skipping 44 matching lines @@
   size_t scheduled_raster_task_limit;
   bool use_occlusion_for_tile_prioritization;
   bool record_full_layer;
 
   LayerTreeDebugState initial_debug_state;
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_SETTINGS_H_