Add an experiment to redirect SequencedWorkerPool tasks to TaskScheduler.

base/threading/sequenced_worker_pool.h

 // Copyright (c) 2012 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.
 
 #ifndef BASE_THREADING_SEQUENCED_WORKER_POOL_H_
 #define BASE_THREADING_SEQUENCED_WORKER_POOL_H_
 
 #include <stddef.h>
 
 #include <cstddef>
@@ skipping 154 matching lines @@
   static SequenceToken GetSequenceTokenForCurrentThread();
 
   // Returns the SequencedWorkerPool that owns this thread, or null if the
   // current thread is not a SequencedWorkerPool worker thread.
   static scoped_refptr<SequencedWorkerPool> GetWorkerPoolForCurrentThread();
 
   // Returns a unique token that can be used to sequence tasks posted to
   // 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.
+  // TODO(gab): Remove this if http://crbug.com/622400 fails
+  // (SequencedWorkerPool will be phased out completely otherwise).
+  static void RedirectSequencedWorkerPoolsToTaskSchedulerForProcess();
+
   // When constructing a SequencedWorkerPool, there must be a
   // ThreadTaskRunnerHandle on the current thread unless you plan to
   // deliberately leak it.
 
   // Pass the maximum number of threads (they will be lazily created as needed)
   // and a prefix for the thread name to aid in debugging. |task_priority| will
   // be used to hint base::TaskScheduler for an experiment in which all
   // SequencedWorkerPool tasks will be redirected to it in processes where a
   // base::TaskScheduler was instantiated.
   SequencedWorkerPool(size_t max_threads,
@@ skipping 189 matching lines @@
   // Avoid pulling in too many headers by putting (almost) everything
   // into |inner_|.
   const std::unique_ptr<Inner> inner_;
 
   DISALLOW_COPY_AND_ASSIGN(SequencedWorkerPool);
 };
 
 }  // namespace base
 
 #endif  // BASE_THREADING_SEQUENCED_WORKER_POOL_H_