Make swapping the incoming queue with the work queue constant time....

base/message_loop.cc

Index: base/message_loop.cc
===================================================================
--- base/message_loop.cc	(revision 25087)
+++ base/message_loop.cc	(working copy)
@@ -354,7 +354,7 @@
     AutoLock lock(incoming_queue_lock_);
     if (incoming_queue_.empty())
       return;
-    std::swap(incoming_queue_, work_queue_);
+    incoming_queue_.Swap(&work_queue_);  // Constant time
     DCHECK(incoming_queue_.empty());
   }
 }