Make RunLoop remove handle when a timeout is notified

mojo/public/utility/run_loop.h

Index: mojo/public/utility/run_loop.h
diff --git a/mojo/public/utility/run_loop.h b/mojo/public/utility/run_loop.h
index 839d6de26743fb701f55da0cb02c83103d323ecb..a0c4d70e56459b84b984a812a1829f77ee4330fd 100644
--- a/mojo/public/utility/run_loop.h
+++ b/mojo/public/utility/run_loop.h
@@ -37,6 +37,7 @@ class RunLoop {
                   MojoWaitFlags wait_flags,
                   MojoDeadline deadline);
   void RemoveHandler(const Handle& handle);
+  bool HasHandler(const Handle& handle) const;
 
   // Runs the loop servicing handles as they are ready. This returns when Quit()
   // is invoked, or there no more handles.