Add an experiment to redirect DOMStorageTaskRunner to TaskScheduler.

content/browser/dom_storage/dom_storage_task_runner.h

 // Copyright 2013 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 CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_TASK_RUNNER_H_
 #define CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_TASK_RUNNER_H_
 
 #include "base/memory/ref_counted.h"
 #include "base/sequence_checker.h"
 #include "base/sequenced_task_runner.h"
-#include "base/single_thread_task_runner.h"
-#include "base/threading/sequenced_worker_pool.h"
 #include "base/time/time.h"
 #include "content/common/content_export.h"
 
-namespace base {
-class SingleThreadTaskRunner;
-}
-
 namespace content {
 
 // DOMStorage uses two task sequences (primary vs commit) to avoid
 // primary access from queuing up behind commits to disk.
 // * Initialization, shutdown, and administrative tasks are performed as
 //   shutdown-blocking primary sequence tasks.
 // * Tasks directly related to the javascript'able interface are performed
 //   as shutdown-blocking primary sequence tasks.
 //   TODO(michaeln): Skip tasks for reading during shutdown.
 // * Internal tasks related to committing changes to disk are performed as
@@ skipping 21 matching lines @@
   virtual void AssertIsRunningOnPrimarySequence() const = 0;
   virtual void AssertIsRunningOnCommitSequence() const = 0;
 
   virtual scoped_refptr<base::SequencedTaskRunner> GetSequencedTaskRunner(
       SequenceID sequence_id) = 0;
 
  protected:
   ~DOMStorageTaskRunner() override {}
 };
 
-// A derived class used in chromium that utilizes a SequenceWorkerPool
-// under dom_storage specific SequenceTokens. The |delayed_task_loop|
-// is used to delay scheduling on the worker pool.
+// A DOMStorageTaskRunner which manages a primary and a commit sequence.
 class CONTENT_EXPORT DOMStorageWorkerPoolTaskRunner :
       public DOMStorageTaskRunner {
  public:
+  // |primary_sequence| and |commit_sequence| should have
+  // TaskShutdownBehaviour::BLOCK_SHUTDOWN semantics.
   DOMStorageWorkerPoolTaskRunner(
-      base::SequencedWorkerPool* sequenced_worker_pool,
-      base::SequencedWorkerPool::SequenceToken primary_sequence_token,
-      base::SequencedWorkerPool::SequenceToken commit_sequence_token,
-      base::SingleThreadTaskRunner* delayed_task_task_runner);
+      scoped_refptr<base::SequencedTaskRunner> primary_sequence,
+      scoped_refptr<base::SequencedTaskRunner> commit_sequence);
 
   bool RunsTasksOnCurrentThread() const override;
 
   bool PostDelayedTask(const tracked_objects::Location& from_here,
                        const base::Closure& task,
                        base::TimeDelta delay) override;
 
   bool PostShutdownBlockingTask(const tracked_objects::Location& from_here,
                                 SequenceID sequence_id,
                                 const base::Closure& task) override;
 
   void AssertIsRunningOnPrimarySequence() const override;
   void AssertIsRunningOnCommitSequence() const override;
 
   scoped_refptr<base::SequencedTaskRunner> GetSequencedTaskRunner(
       SequenceID sequence_id) override;
 
  protected:
   ~DOMStorageWorkerPoolTaskRunner() override;
 
  private:
+  scoped_refptr<base::SequencedTaskRunner> primary_sequence_;
+  scoped_refptr<base::SequencedTaskRunner> commit_sequence_;
 
-  base::SequencedWorkerPool::SequenceToken IDtoToken(SequenceID id) const;
-
-  const scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
-  const scoped_refptr<base::SequencedWorkerPool> sequenced_worker_pool_;
-  base::SequencedWorkerPool::SequenceToken primary_sequence_token_;
-  base::SequenceChecker primary_sequence_checker_;
-  base::SequencedWorkerPool::SequenceToken commit_sequence_token_;
-  base::SequenceChecker commit_sequence_checker_;
+  DISALLOW_COPY_AND_ASSIGN(DOMStorageWorkerPoolTaskRunner);
 };
 
 // A derived class used in unit tests that ignores all delays so
 // we don't block in unit tests waiting for timeouts to expire.
 // There is no distinction between [non]-shutdown-blocking or
 // the primary sequence vs the commit sequence in the mock,
-// all tasks are scheduled on |message_loop| with zero delay.
+// all tasks are scheduled on |task_runner| with zero delay.
 class CONTENT_EXPORT MockDOMStorageTaskRunner :
       public DOMStorageTaskRunner {
  public:
-  explicit MockDOMStorageTaskRunner(base::SingleThreadTaskRunner* task_runner);
+  explicit MockDOMStorageTaskRunner(
+      scoped_refptr<base::SequencedTaskRunner> task_runner);
 
   bool RunsTasksOnCurrentThread() const override;
 
   bool PostDelayedTask(const tracked_objects::Location& from_here,
                        const base::Closure& task,
                        base::TimeDelta delay) override;
 
   bool PostShutdownBlockingTask(const tracked_objects::Location& from_here,
                                 SequenceID sequence_id,
                                 const base::Closure& task) override;
 
   void AssertIsRunningOnPrimarySequence() const override;
   void AssertIsRunningOnCommitSequence() const override;
 
   scoped_refptr<base::SequencedTaskRunner> GetSequencedTaskRunner(
       SequenceID sequence_id) override;
 
  protected:
   ~MockDOMStorageTaskRunner() override;
 
  private:
-  const scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  const scoped_refptr<base::SequencedTaskRunner> task_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(MockDOMStorageTaskRunner);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_TASK_RUNNER_H_