Add SequencedTaskRunnerHandle to get a SequencedTaskRunner for the current thread / sequence.

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 ee282bc231207ec18b511ab51dfe5eb9fee93306..558712816bf69f375b7e39312389620c9d496d75 100644
--- a/base/threading/sequenced_worker_pool.h
+++ b/base/threading/sequenced_worker_pool.h
@@ -130,11 +130,19 @@ class BASE_EXPORT SequencedWorkerPool : public TaskRunner {
       return id_ == other.id_;
     }
 
+    bool operator==(const SequenceToken& other) const {
+      return Equals(other);
+    }
+
     // Returns false if current thread is executing an unsequenced task.
     bool IsValid() const {
       return id_ != 0;
     }
 
+    // Returns a string representation of this token. This method should only be
+    // used for debugging.
+    std::string ToString() const;
+
    private:
     friend class SequencedWorkerPool;
 
@@ -157,12 +165,16 @@ class BASE_EXPORT SequencedWorkerPool : public TaskRunner {
   // an unsequenced task, returns an invalid SequenceToken.
   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();
+
   // When constructing a SequencedWorkerPool, there must be a
-  // MessageLoop on the current thread unless you plan to deliberately
-  // leak it.
+  // 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.
+  // Pass the maximum number of threads (they will be lazily created as
+  // needed) and a prefix for the thread name to aid in debugging.
   SequencedWorkerPool(size_t max_threads,
                       const std::string& thread_name_prefix);
 
@@ -355,6 +367,12 @@ class BASE_EXPORT SequencedWorkerPool : public TaskRunner {
   DISALLOW_COPY_AND_ASSIGN(SequencedWorkerPool);
 };
 
+// Stream operator to allow using a SequenceToken in a DCHECK or testing
+// assertion.
+BASE_EXPORT std::ostream& operator<<(
+    std::ostream& out,
+    const SequencedWorkerPool::SequenceToken& token);
+
 }  // namespace base
 
 #endif  // BASE_THREADING_SEQUENCED_WORKER_POOL_H_