[Sync] Split DirectoryChangeListener for thread-safety

base/observer_list_threadsafe.h

Index: base/observer_list_threadsafe.h
diff --git a/base/observer_list_threadsafe.h b/base/observer_list_threadsafe.h
index 883e28503e575939c54d3f1fb2aba596bd2677fc..cb7de037f4de540700ae700381203625526d103f 100644
--- a/base/observer_list_threadsafe.h
+++ b/base/observer_list_threadsafe.h
@@ -153,6 +153,27 @@ class ObserverListThreadSafe
     Notify<Method, Tuple1<A> >(method);
   }
 
+  template <class Method, class A, class B>
+  void Notify(Method m, const A &a, const B &b) {
+    UnboundMethod<ObserverType, Method, Tuple2<A, B> > method(
+        m, MakeTuple(a, b));
+    Notify<Method, Tuple2<A, B> >(method);
+  }
+
+  template <class Method, class A, class B, class C>
+  void Notify(Method m, const A &a, const B &b, const C &c) {
+    UnboundMethod<ObserverType, Method, Tuple3<A, B, C> > method(
+        m, MakeTuple(a, b, c));
+    Notify<Method, Tuple3<A, B, C> >(method);
+  }
+
+  template <class Method, class A, class B, class C, class D>
+  void Notify(Method m, const A &a, const B &b, const C &c, const D &d) {
+    UnboundMethod<ObserverType, Method, Tuple4<A, B, C, D> > method(
+        m, MakeTuple(a, b, c, d));
+    Notify<Method, Tuple4<A, B, C, D> >(method);
+  }
+
   // TODO(mbelshe):  Add more wrappers for Notify() with more arguments.
 
  private: