Cleanup: Remove NOTIFICATION_EXTENSION_UNLOADED usage in MediaScanManager.

base/scoped_observer.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_SCOPED_OBSERVER_H_
 #define BASE_SCOPED_OBSERVER_H_
 
 #include <algorithm>
 #include <vector>
 
 #include "base/basictypes.h"
 
 // ScopedObserver is used to keep track of the set of sources an object has
 // attached itself to as an observer. When ScopedObserver is destroyed it
 // removes the object as an observer from all sources it has been added to.
 template <class Source, class Observer>
 class ScopedObserver {
  public:
   explicit ScopedObserver(Observer* observer) : observer_(observer) {}
 
   ~ScopedObserver() {
-    for (size_t i = 0; i < sources_.size(); ++i)
-      sources_[i]->RemoveObserver(observer_);
+    RemoveAll();
   }
 
   // Adds the object passed to the constructor as an observer on |source|.
   void Add(Source* source) {
     sources_.push_back(source);
     source->AddObserver(observer_);
   }
 
   // Remove the object passed to the constructor as an observer from |source|.
   void Remove(Source* source) {
     sources_.erase(std::find(sources_.begin(), sources_.end(), source));
     source->RemoveObserver(observer_);
   }
 
+  void RemoveAll() {
+    for (size_t i = 0; i < sources_.size(); ++i)
+      sources_[i]->RemoveObserver(observer_);
+    sources_.clear();
+  }
+
   bool IsObserving(Source* source) const {
-    for (size_t i = 0; i < sources_.size(); ++i) {
-      if (sources_[i] == source)
-        return true;
-    }
-    return false;
+    return std::find(sources_.begin(), sources_.end(), source) !=
+        sources_.end();
   }
 
  private:
   Observer* observer_;
 
   std::vector<Source*> sources_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedObserver);
 };
 
 #endif  // BASE_SCOPED_OBSERVER_H_