Test SequencedWorkerPool with redirection to the TaskScheduler.

base/threading/sequenced_worker_pool.h

Index: base/threading/sequenced_worker_pool.h
diff --git a/base/threading/sequenced_worker_pool.h b/base/threading/sequenced_worker_pool.h
index 0e916c8782bbfe9e0230e2ec1a73d32f0a513680..9e7984df93fd74de7f1b220d677051dc2c15cb2d 100644
--- a/base/threading/sequenced_worker_pool.h
+++ b/base/threading/sequenced_worker_pool.h
@@ -172,16 +172,28 @@ class BASE_EXPORT SequencedWorkerPool : public TaskRunner {
   // PostSequencedWorkerTask(). Valid tokens are always nonzero.
   static SequenceToken GetSequenceToken();
 
-  // Invoke this once on the main thread of a process, before any other threads
-  // are created and before any tasks are posted to that process'
-  // SequencedWorkerPools but after TaskScheduler was instantiated, to force all
-  // SequencedWorkerPools in that process to redirect their tasks to the
-  // TaskScheduler. Note: SequencedWorkerPool instances with |max_threads == 1|
-  // will be special cased to send all of their work as
-  // ExecutionMode::SINGLE_THREADED.
+  // Invoke this to start redirecting tasks posted to this process'
+  // SequencedWorkerPools to the registered TaskScheduler. This cannot be called
+  // after a task has been posted to a SequencedWorkerPool. This is not thread-
+  // safe; proper synchronization is required to use any method of
+  // SequencedWorkerPool after calling this. There must be a registered
+  // TaskScheduler when this is called. Ideally, call this on the main thread of
+  // a process, before any other threads are created and before any tasks are
+  // posted to that process' SequencedWorkerPools.
+  // Note: SequencedWorkerPool instances with |max_threads == 1| will be special
+  // cased to send all of their work as ExecutionMode::SINGLE_THREADED.
   // TODO(gab): Remove this if http://crbug.com/622400 fails
   // (SequencedWorkerPool will be phased out completely otherwise).
-  static void RedirectSequencedWorkerPoolsToTaskSchedulerForProcess();
+  static void RedirectToTaskSchedulerForProcess();
+
+  // Stops redirecting tasks posted to this process' SequencedWorkerPools to the
+  // registered TaskScheduler. Also allows RedirectToTaskSchedulerForProcess()
+  // to be called again after tasks have been posted to this process'
+  // SequencedWorkerPools. Calling this while there are active
+  // SequencedWorkerPools isn't supported. This is not thread-safe; proper
+  // synchronization is required to call any method of SequencedWorkerPool after
+  // calling this.
+  static void ResetRedirectToTaskSchedulerForProcessForTesting();
 
   // When constructing a SequencedWorkerPool, there must be a
   // ThreadTaskRunnerHandle on the current thread unless you plan to