[Sync] Split DirectoryChangeListener for thread-safety

base/observer_list_threadsafe.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_OBSERVER_LIST_THREADSAFE_H_
 #define BASE_OBSERVER_LIST_THREADSAFE_H_
 #pragma once
 
 #include <algorithm>
 #include <map>
@@ skipping 130 matching lines @@
   // Note, these calls are effectively asynchronous.  You cannot assume
   // that at the completion of the Notify call that all Observers have
   // been Notified.  The notification may still be pending delivery.
   template <class Method>
   void Notify(Method m) {
     UnboundMethod<ObserverType, Method, Tuple0> method(m, MakeTuple());
     Notify<Method, Tuple0>(method);
   }
 
   template <class Method, class A>
-  void Notify(Method m, const A &a) {
+  void Notify(Method m, const A& a) {
     UnboundMethod<ObserverType, Method, Tuple1<A> > method(m, MakeTuple(a));
     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:
   // See comment above ObserverListThreadSafeTraits' definition.
   friend struct ObserverListThreadSafeTraits<ObserverType>;
 
   ~ObserverListThreadSafe() {
     typename ObserversListMap::const_iterator it;
     for (it = observer_lists_.begin(); it != observer_lists_.end(); ++it)
       delete (*it).second;
@@ skipping 63 matching lines @@
 
   // These are marked mutable to facilitate having NotifyAll be const.
   base::Lock list_lock_;  // Protects the observer_lists_.
   ObserversListMap observer_lists_;
   const NotificationType type_;
 
   DISALLOW_COPY_AND_ASSIGN(ObserverListThreadSafe);
 };
 
 #endif  // BASE_OBSERVER_LIST_THREADSAFE_H_