cc: Introduce forward_begin_frames_to_children and use_external_begin_frame_source

cc/trees/layer_tree_settings.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_settings.h"
 
 #include <limits>
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
 
 namespace cc {
 
 LayerTreeSettings::LayerTreeSettings()
     : impl_side_painting(false),
       allow_antialiasing(true),
       force_antialiasing(false),
       force_blending_with_shaders(false),
       throttle_frame_production(true),
       single_thread_proxy_scheduler(true),
-      begin_frame_scheduling_enabled(false),
+      use_external_begin_frame_source(false),
+      forward_begin_frames_to_children(false),
       main_frame_before_activation_enabled(false),
       using_synchronous_renderer_compositor(false),
       disable_hi_res_timer_tasks_on_battery(false),
       report_overscroll_only_for_scrollable_axes(false),
       per_tile_painting_enabled(false),
       partial_swap_enabled(false),
       accelerated_animation_enabled(true),
       can_use_lcd_text(true),
       use_distance_field_text(false),
       should_clear_root_render_pass(true),
@@ skipping 37 matching lines @@
       use_rgba_4444_textures(false),
       texture_id_allocation_chunk_size(64),
       scheduled_raster_task_limit(32),
       use_occlusion_for_tile_prioritization(false),
       record_full_layer(false) {
 }
 
 LayerTreeSettings::~LayerTreeSettings() {}
 
 }  // namespace cc