cc: Adding BeginFrameTracker object and removing Now() from LTHI.

cc/BUILD.gn

 # Copyright 2014 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.
 
 component("cc") {
   sources = [
     "animation/animation.cc",
     "animation/animation.h",
     "animation/animation_curve.cc",
     "animation/animation_curve.h",
@@ skipping 444 matching lines @@
     "resources/ui_resource_bitmap.h",
     "resources/ui_resource_client.h",
     "resources/ui_resource_request.cc",
     "resources/ui_resource_request.h",
     "resources/video_resource_updater.cc",
     "resources/video_resource_updater.h",
     "resources/zero_copy_tile_task_worker_pool.cc",
     "resources/zero_copy_tile_task_worker_pool.h",
     "scheduler/begin_frame_source.cc",
     "scheduler/begin_frame_source.h",
+    "scheduler/begin_frame_tracker.cc",
+    "scheduler/begin_frame_tracker.h",
     "scheduler/delay_based_time_source.cc",
     "scheduler/delay_based_time_source.h",
     "scheduler/draw_result.h",
     "scheduler/scheduler.cc",
     "scheduler/scheduler.h",
     "scheduler/scheduler_settings.cc",
     "scheduler/scheduler_settings.h",
     "scheduler/scheduler_state_machine.cc",
     "scheduler/scheduler_state_machine.h",
     "trees/blocking_task_runner.cc",
@@ skipping 400 matching lines @@
     "//media",
     "//skia",
     "//testing/gmock",
     "//testing/gtest",
     "//testing/perf",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/gl",
   ]
 }