Make SequencedWorkerPool a TaskRunner

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_
 #pragma once
 
 #include <cstddef>
 #include <list>
 #include <map>
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/atomicops.h"
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/callback.h"
+#include "base/compiler_specific.h"
 #include "base/memory/linked_ptr.h"
-#include "base/memory/ref_counted.h"
 #include "base/synchronization/condition_variable.h"
 #include "base/synchronization/lock.h"
+#include "base/task_runner.h"
 #include "base/tracked_objects.h"
 
 namespace base {
 
 // A worker thread pool that enforces ordering between sets of tasks. It also
 // allows you to specify what should happen to your tasks on shutdown.
 //
 // To enforce ordering, get a unique sequence token from the pool and post all
 // tasks you want to order with the token. All tasks with the same token are
 // guaranteed to execute serially, though not necessarily on the same thread.
@@ skipping 14 matching lines @@
 //
 // This class is designed to be leaked on shutdown to allow the
 // CONTINUE_ON_SHUTDOWN behavior to be implemented. To enforce the
 // BLOCK_SHUTDOWN behavior, you must call Shutdown() which will wait until
 // the necessary tasks have completed.
 //
 // Implementation note: This does not use a base::WorkerPool since that does
 // not enforce shutdown semantics or allow us to specify how many worker
 // threads to run. For the typical use case of random background work, we don't
 // necessarily want to be super aggressive about creating threads.
-class BASE_EXPORT SequencedWorkerPool
-    : public RefCountedThreadSafe<SequencedWorkerPool> {
+//
+// Note that SequencedWorkerPool is RefCountedThreadSafe (inherited
+// from TaskRunner).
+class BASE_EXPORT SequencedWorkerPool : public TaskRunner {
  public:
   // Defines what should happen to a task posted to the worker pool on shutdown.
   enum WorkerShutdown {
     // Tasks posted with this mode which have not run at shutdown will be
     // deleted rather than run, and any tasks with this mode running at
     // shutdown will be ignored (the worker thread will not be joined).
     //
     // This option provides a nice way to post stuff you don't want blocking
     // shutdown. For example, you might be doing a slow DNS lookup and if it's
     // blocked on the OS, you may not want to stop shutdown, since the result
@@ skipping 118 matching lines @@
                                     const Closure& task);
 
   // Same as PostSequencedWorkerTask but allows specification of the shutdown
   // behavior.
   bool PostSequencedWorkerTaskWithShutdownBehavior(
       SequenceToken sequence_token,
       const tracked_objects::Location& from_here,
       const Closure& task,
       WorkerShutdown shutdown_behavior);
 
+  // TaskRunner implementation.  Forwards to PostWorkerTask().
+  virtual bool PostDelayedTask(const tracked_objects::Location& from_here,
+                               const Closure& task,
+                               int64 delay_ms) OVERRIDE;
+  virtual bool RunsTasksOnCurrentThread() const OVERRIDE;
+
   // Blocks until all pending tasks are complete. This should only be called in
   // unit tests when you want to validate something that should have happened.
   //
   // Note that calling this will not prevent other threads from posting work to
   // the queue while the calling thread is waiting on Flush(). In this case,
   // Flush will return only when there's no more work in the queue. Normally,
   // this doesn't come up sine in a test, all the work is being posted from
   // the main thread.
   void FlushForTesting();
 
   // Implements the worker pool shutdown. This should be called during app
   // shutdown, and will discard/join with appropriate tasks before returning.
   // After this call, subsequent calls to post tasks will fail.
   void Shutdown();
 
   // Called by tests to set the testing observer. This is NULL by default
   // and ownership of the pointer is kept with the caller.
   void SetTestingObserver(TestingObserver* observer);
 
+ protected:
+  virtual ~SequencedWorkerPool();
+
  private:
-  friend class RefCountedThreadSafe<SequencedWorkerPool>;
   class Worker;
 
   struct SequencedTask {
     SequencedTask();
     ~SequencedTask();
 
     int sequence_token_id;
     WorkerShutdown shutdown_behavior;
     tracked_objects::Location location;
     Closure task;
   };
 
-  ~SequencedWorkerPool();
-
   // This function accepts a name and an ID. If the name is null, the
   // token ID is used. This allows us to implement the optional name lookup
   // from a single function without having to enter the lock a separate time.
   bool PostTaskHelper(const std::string* optional_token_name,
                       SequenceToken sequence_token,
                       WorkerShutdown shutdown_behavior,
                       const tracked_objects::Location& from_here,
                       const Closure& task);
 
   // Runs the worker loop on the background thread.
@@ skipping 101 matching lines @@
   bool shutdown_called_;
 
   TestingObserver* testing_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(SequencedWorkerPool);
 };
 
 }  // namespace base
 
 #endif  // BASE_THREADING_SEQUENCED_WORKER_POOL_H_