Add testRunner.runIdleTasks() to force idle tasks to run.

components/scheduler/child/idle_helper.cc

Index: components/scheduler/child/idle_helper.cc
diff --git a/components/scheduler/child/idle_helper.cc b/components/scheduler/child/idle_helper.cc
index e64be4fe22488464fdfcdf6b2781fafed24a38cb..1cbeabd9075721cf7644c657d65fb610610b0dae 100644
--- a/components/scheduler/child/idle_helper.cc
+++ b/components/scheduler/child/idle_helper.cc
@@ -15,6 +15,51 @@
 
 namespace scheduler {
 
+namespace {
+
+class IdleTaskObserverForTesting
+    : public base::MessageLoop::TaskObserver {
+ public:
+  IdleTaskObserverForTesting(
+      scoped_refptr<TaskQueue> idle_queue,
+      SchedulerHelper* helper,
+      const base::Closure& finished_callback);
+  void WillProcessTask(const base::PendingTask& pending_task) override;
+  void DidProcessTask(const base::PendingTask& pending_task) override;
+ private:
+  scoped_refptr<TaskQueue> idle_queue_;
+  SchedulerHelper* helper_;
+  base::Closure finished_callback_;
+};
+
+IdleTaskObserverForTesting::IdleTaskObserverForTesting(
+    scoped_refptr<TaskQueue> idle_queue,
+    SchedulerHelper* helper,
+    const base::Closure& finished_callback)
+  : idle_queue_(idle_queue),
+    helper_(helper),
+    finished_callback_(finished_callback) {
+  helper_->AddTaskObserver(this);
+}
+
+void IdleTaskObserverForTesting::WillProcessTask(
+    const base::PendingTask& pending_task) {
+}
+
+void IdleTaskObserverForTesting::DidProcessTask(
+    const base::PendingTask& pending_task)
+{
+  if (idle_queue_->IsEmpty()) {
+    idle_queue_->SetQueueEnabled(false);
+    helper_->DefaultTaskRunner()->PostTask(
+        FROM_HERE, finished_callback_);
+    helper_->RemoveTaskObserver(this);
+    delete this;
+  }
+}
+
+}
+
 IdleHelper::IdleHelper(
     SchedulerHelper* helper,
     Delegate* delegate,
@@ -482,4 +527,10 @@ const char* IdleHelper::IdlePeriodStateToString(
   }
 }
 
+void IdleHelper::RunIdleTasksForTesting(const base::Closure& callback) {
+  new IdleTaskObserverForTesting(idle_queue_, helper_, callback);

[szager1, 2016/03/23 22:55:13]

This is intentional; the instance gets deleted in
IdleTaskObserverForTesting::DidProcessTask.

[Sami, 2016/03/29 11:11:17]

Instead of using an observer, it might be easier just to post an extra idle task
here which invokes the finished callback. (Actually the caller could do that too
which would reduce some of the plumbing here.)

[szager1, 2016/04/06 08:43:17]

Done; I was able to get rid of all changes to IdleHelper.

+  idle_queue_->SetQueueEnabled(true);

[Sami, 2016/03/29 11:11:17]

I think one problem here is that IdleHelper might disable the queue while we're
in the middle of running tasks for tests. Maybe we should add a new flag which
tells the helper that we're flushing idle tasks so it knows to avoid messing
with the queue state?

[szager1, 2016/04/06 08:43:17]

Done; added the field in_idle_period_for_testing to struct MainThreadOnly in
RendererSchedulerImp.

+  idle_queue_->PumpQueue(true);
+}
+
 }  // namespace scheduler