Make SequencedWorkerPool a TaskRunner

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 2bd3d581f5fb52eeac54c9d8ca229df9f115c603..dff01785850edcb868132cac0b3703f1f905832b 100644
--- a/base/threading/sequenced_worker_pool.h
+++ b/base/threading/sequenced_worker_pool.h
@@ -17,10 +17,11 @@
 #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 {
@@ -55,8 +56,10 @@ namespace base {
 // 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 {
@@ -195,6 +198,12 @@ class BASE_EXPORT SequencedWorkerPool
       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.
   //
@@ -214,8 +223,10 @@ class BASE_EXPORT SequencedWorkerPool
   // 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 {
@@ -228,8 +239,6 @@ class BASE_EXPORT SequencedWorkerPool
     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.