Investigate Android build problems in review 1414463004.

base/observer_list_threadsafe.h

 // Copyright (c) 2012 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_
 
 #include <algorithm>
 #include <map>
 
@@ skipping 93 matching lines @@
  public:
   typedef typename ObserverList<ObserverType>::NotificationType
       NotificationType;
 
   ObserverListThreadSafe()
       : type_(ObserverListBase<ObserverType>::NOTIFY_ALL) {}
   explicit ObserverListThreadSafe(NotificationType type) : type_(type) {}
 
   // Add an observer to the list.  An observer should not be added to
   // the same list more than once.
-  void AddObserver(ObserverType* obs) {
+  bool AddObserver(ObserverType* obs) {
     // If there is not a current MessageLoop, it is impossible to notify on it,
     // so do not add the observer.
     if (!MessageLoop::current())
-      return;
+      return false;
 
     ObserverList<ObserverType>* list = nullptr;
     PlatformThreadId thread_id = PlatformThread::CurrentId();
     {
       AutoLock lock(list_lock_);
       if (observer_lists_.find(thread_id) == observer_lists_.end())
         observer_lists_[thread_id] = new ObserverListContext(type_);
       list = &(observer_lists_[thread_id]->list);
     }
     list->AddObserver(obs);
+    return true;
   }
 
   // Remove an observer from the list if it is in the list.
   // If there are pending notifications in-transit to the observer, they will
   // be aborted.
   // If the observer to be removed is in the list, RemoveObserver MUST
   // be called from the same thread which called AddObserver.
   void RemoveObserver(ObserverType* obs) {
     ObserverListContext* context = nullptr;
     ObserverList<ObserverType>* list = nullptr;
@@ skipping 124 matching lines @@
   mutable Lock list_lock_;  // Protects the observer_lists_.
   ObserversListMap observer_lists_;
   const NotificationType type_;
 
   DISALLOW_COPY_AND_ASSIGN(ObserverListThreadSafe);
 };
 
 }  // namespace base
 
 #endif  // BASE_OBSERVER_LIST_THREADSAFE_H_