POC: Instrument task time tracker

components/scheduler/BUILD.gn

 # 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.
 
 # GYP version: components/scheduler.gypi:scheduler
 component("scheduler") {
   sources = [
     "base/cancelable_closure_holder.cc",
     "base/cancelable_closure_holder.h",
     "base/enqueue_order.cc",
     "base/enqueue_order.h",
     "base/lazy_now.cc",
     "base/lazy_now.h",
     "base/pollable_thread_safe_flag.cc",
     "base/pollable_thread_safe_flag.h",
     "base/real_time_domain.cc",
     "base/real_time_domain.h",
     "base/task_queue.h",
     "base/task_queue_impl.cc",
     "base/task_queue_impl.h",
     "base/task_queue_manager.cc",
     "base/task_queue_manager.h",
     "base/task_queue_manager_delegate.h",
     "base/task_queue_selector.cc",
     "base/task_queue_selector.h",
+    "base/task_time_tracker.cc",
+    "base/task_time_tracker.h",
     "base/time_domain.cc",
     "base/time_domain.h",
     "base/virtual_time_domain.cc",
     "base/virtual_time_domain.h",
     "base/work_queue.cc",
     "base/work_queue.h",
     "base/work_queue_sets.cc",
     "base/work_queue_sets.h",
     "child/child_scheduler.h",
     "child/compositor_worker_scheduler.cc",
@@ skipping 133 matching lines @@
 
   deps = [
     "//third_party/WebKit/public:blink",
   ]
 
   public_deps = [
     ":scheduler",
     "//base",
   ]
 }