[scheduler] Always run task queue observer callback for delayed work.

Run task queue observer callback even when there is immediate work
availaible. This will prevent some renderers from stucking in a
throttled state with a fence.

This is a temporary solution enabling delphick@ to revert his patch.
A proper fix and test coverage will come later.

R=skyostil@chromium.org
CC=delphick@chromium.org
BUG=710095

Review-Url: https://codereview.chromium.org/2844223004
Cr-Commit-Position: refs/heads/master@{#467956}

third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.cc

@@ -890,10 +890,8 @@ void TaskQueueImpl::ScheduleDelayedWorkInTimeDomain(base::TimeTicks now) {
       this, main_thread_only().delayed_incoming_queue.top().delayed_wake_up(),
       now);
 
-  if (!HasPendingImmediateWork()) {
-    NotifyWakeUpChangedOnMainThread(
-        main_thread_only().delayed_incoming_queue.top().delayed_run_time);
-  }
+  NotifyWakeUpChangedOnMainThread(
+      main_thread_only().delayed_incoming_queue.top().delayed_run_time);
 }
 
 void TaskQueueImpl::NotifyWakeUpChangedOnMainThread(base::TimeTicks wake_up) {