scheduler: Disable expensive timers during main thread user input

components/scheduler/child/task_queue_impl.cc

 // 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.
 
 #include "components/scheduler/child/task_queue_impl.h"
 
 #include "components/scheduler/child/task_queue_manager.h"
 
 namespace scheduler {
 namespace internal {
@@ skipping 419 matching lines @@
     state->EndArray();
     state->BeginArray("delayed_task_queue");
     QueueAsValueInto(delayed_task_queue_, state);
     state->EndArray();
   }
   state->SetString("priority",
                    PriorityToString(static_cast<QueuePriority>(set_index_)));
   state->EndDictionary();
 }
 
+void TaskQueueImpl::AddTaskObserver(
+    base::MessageLoop::TaskObserver* task_observer) {
+  DCHECK(main_thread_checker_.CalledOnValidThread());
+  task_observers_.AddObserver(task_observer);
+}
+
+void TaskQueueImpl::RemoveTaskObserver(
+    base::MessageLoop::TaskObserver* task_observer) {
+  DCHECK(main_thread_checker_.CalledOnValidThread());
+  task_observers_.RemoveObserver(task_observer);
+}
+
+void TaskQueueImpl::NotifyWillProcessTask(
+    const base::PendingTask& pending_task) {
+  DCHECK(main_thread_checker_.CalledOnValidThread());
+  DCHECK(should_notify_observers_);
+  FOR_EACH_OBSERVER(base::MessageLoop::TaskObserver, task_observers_,
+                    WillProcessTask(pending_task));
+}
+
+void TaskQueueImpl::NotifyDidProcessTask(
+    const base::PendingTask& pending_task) {
+  DCHECK(main_thread_checker_.CalledOnValidThread());
+  DCHECK(should_notify_observers_);
+  FOR_EACH_OBSERVER(base::MessageLoop::TaskObserver, task_observers_,
+                    DidProcessTask(pending_task));
+}
+
 // static
 void TaskQueueImpl::QueueAsValueInto(const std::queue<Task>& queue,
                                      base::trace_event::TracedValue* state) {
   std::queue<Task> queue_copy(queue);
   while (!queue_copy.empty()) {
     TaskAsValueInto(queue_copy.front(), state);
     queue_copy.pop();
   }
 }
 
@@ skipping 17 matching lines @@
   state->SetBoolean("nestable", task.nestable);
   state->SetBoolean("is_high_res", task.is_high_res);
   state->SetDouble(
       "delayed_run_time",
       (task.delayed_run_time - base::TimeTicks()).InMicroseconds() / 1000.0L);
   state->EndDictionary();
 }
 
 }  // namespace internal
 }  // namespace scheduler