base: Change WeakPtr to use SequenceChecker instead of ThreadChecker.

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 7e04b071428c838dfcec0faa647f82baf2932045..fa3fa7a99f311d1b4aa78f558fab0267c1f86519 100644
--- a/base/threading/sequenced_worker_pool.h
+++ b/base/threading/sequenced_worker_pool.h
@@ -143,6 +143,9 @@ class BASE_EXPORT SequencedWorkerPool : public TaskRunner {
     virtual void OnDestruct() = 0;
   };
 
+  // Gets the SequencedWorkerPool for the current thread. Result may be NULL.
+  static SequencedWorkerPool* Current();

[akalin, 2013/06/28 23:32:00]

i don't really like exposing this. seems better to me to just expose the
sequence token. Can't we use the thread id name manager?

[tommycli, 2013/06/28 23:49:49]

Since SequencedWorkerPool is not enforced to be a singleton, there could
theoretically be two different threads owned by two different
SequenceWorkerPools with the same SequenceToken. What do you think?

+
   // When constructing a SequencedWorkerPool, there must be a
   // MessageLoop on the current thread unless you plan to deliberately
   // leak it.
@@ -159,7 +162,7 @@ class BASE_EXPORT SequencedWorkerPool : public TaskRunner {
                       TestingObserver* observer);
 
   // Returns a unique token that can be used to sequence tasks posted to
-  // PostSequencedWorkerTask(). Valid tokens are alwys nonzero.
+  // PostSequencedWorkerTask(). Valid tokens are always nonzero.
   SequenceToken GetSequenceToken();
 
   // Returns the sequence token associated with the given name. Calling this
@@ -168,6 +171,11 @@ class BASE_EXPORT SequencedWorkerPool : public TaskRunner {
   // will be created.
   SequenceToken GetNamedSequenceToken(const std::string& name);
 
+  // Retrieves the sequence token associated with the current thread.
+  // If current thread is not part in worker pool, this returns false and
+  // |result_token| is unmodified. |result_token| may not be NULL.
+  bool GetCurrentThreadSequenceToken(SequenceToken* result_token) const;
+
   // Returns a SequencedTaskRunner wrapper which posts to this
   // SequencedWorkerPool using the given sequence token. Tasks with nonzero
   // delay are posted with SKIP_ON_SHUTDOWN behavior and tasks with zero delay