[scheduler]: Fix a bug with non-nestable tasks.

components/scheduler/child/task_queue_manager.cc

Index: components/scheduler/child/task_queue_manager.cc
diff --git a/components/scheduler/child/task_queue_manager.cc b/components/scheduler/child/task_queue_manager.cc
index 1e6b25ea4f4d3d59c10eace066c63957cc3411e1..89f78f367de4918f6aa4f5136fbd0d363f31cdb7 100644
--- a/components/scheduler/child/task_queue_manager.cc
+++ b/components/scheduler/child/task_queue_manager.cc
@@ -301,10 +301,10 @@ bool TaskQueueManager::ProcessTaskFromWorkQueue(
       FOR_EACH_OBSERVER(base::MessageLoop::TaskObserver, task_observers_,
                         DidProcessTask(pending_task));
     }
-
-    pending_task.task.Reset();
-    *out_previous_task = pending_task;
   }
+
+  pending_task.task.Reset();
+  *out_previous_task = pending_task;

[Sami, 2015/08/12 11:47:51]

Hmm, should we just ignore out_previous_task if we decided to actually not run
it? It feels wrong if a non-nestable task will still cause a wakeup even though
we didn't actually run it. WDYT?

I guess one way would be to have this function return a tri-state enum to say
what it actually did.

[rmcilroy, 2015/08/12 13:08:27]

As discussed offline, this might be our only chance to wake up an after wakeup
queue because we will never get notified when the non-nestable task gets run.
Add a comment as discussed.

   return false;
 }