Adds a SHUTDOWN_TASK_QUEUE and a PreShutdown api to the scheduler.

components/scheduler/child/prioritizing_task_queue_selector_unittest.cc

 // Copyright 2014 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/prioritizing_task_queue_selector.h"
 
 #include "base/bind.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
 #include "base/pending_task.h"
@@ skipping 227 matching lines @@
   }
   selector_.SetQueuePriority(1,
                              PrioritizingTaskQueueSelector::CONTROL_PRIORITY);
   for (int i = 0; i < 100; i++) {
     EXPECT_TRUE(selector_.SelectWorkQueueToService(&chosen_queue_index));
     EXPECT_EQ(1ul, chosen_queue_index);
     // Don't remove task from queue to simulate all queues still being full.
   }
 }
 
+TEST_F(PrioritizingTaskQueueSelectorTest, PreShutdownBlocksDisable) {
+  selector_.SetQueuePriority(0, PrioritizingTaskQueueSelector::NORMAL_PRIORITY);
+  selector_.PreShutdown();
+  selector_.DisableQueue(0);
+  EXPECT_TRUE(selector_.IsQueueEnabled(0));
+}
+
+TEST_F(PrioritizingTaskQueueSelectorTest, PreShutdownBlocksSetQueuePriority) {
+  selector_.DisableQueue(0);
+  selector_.PreShutdown();
+  selector_.SetQueuePriority(0, PrioritizingTaskQueueSelector::NORMAL_PRIORITY);
+  EXPECT_FALSE(selector_.IsQueueEnabled(0));
+}
+
+TEST_F(PrioritizingTaskQueueSelectorTest, PreShutdownBlocksEnable) {
+  selector_.DisableQueue(0);
+  selector_.PreShutdown();
+  selector_.EnableQueue(0, PrioritizingTaskQueueSelector::NORMAL_PRIORITY);
+  EXPECT_FALSE(selector_.IsQueueEnabled(0));
+}
+
 }  // namespace scheduler