Report expected task queueing time via UMA

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/queueing_time_estimator.cc",
+    "base/queueing_time_estimator.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.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 75 matching lines @@
   sources = [
     "common/scheduler_switches.cc",
     "common/scheduler_switches.h",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
 
   sources = [
+    "base/queueing_time_estimator_unittest.cc",
     "base/task_queue_manager_delegate_for_test.cc",
     "base/task_queue_manager_delegate_for_test.h",
     "base/task_queue_manager_unittest.cc",
     "base/task_queue_selector_unittest.cc",
-    "base/test_always_fail_time_source.cc",
-    "base/test_always_fail_time_source.h",
+    "base/test_count_uses_time_source.cc",
+    "base/test_count_uses_time_source.h",
+    "base/test_task_time_tracker.h",
     "base/test_time_source.cc",
     "base/test_time_source.h",
     "base/time_domain_unittest.cc",
     "base/work_queue_sets_unittest.cc",
     "child/idle_helper_unittest.cc",
     "child/scheduler_helper_unittest.cc",
     "child/scheduler_tqm_delegate_for_test.cc",
     "child/scheduler_tqm_delegate_for_test.h",
     "child/scheduler_tqm_delegate_impl_unittest.cc",
     "child/webthread_impl_for_worker_scheduler_unittest.cc",
@@ skipping 32 matching lines @@
 
   deps = [
     "//third_party/WebKit/public:blink",
   ]
 
   public_deps = [
     ":scheduler",
     "//base",
   ]
 }