Listen to Off The Record profiles in ContentSettingsHandler.

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"
+#include "base/logging.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() {
     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));
+    auto it = std::find(sources_.begin(), sources_.end(), source);
+    DCHECK(it != sources_.end());

[Lei Zhang, 2014/10/24 19:57:29]

Looking at base/observer_list_unittest.cc, it should be ok to call
RemoveObserver() for something that's not being observed.

[scheib, 2014/10/24 21:46:19]

True, but I think errors such as the previous one in ContentSettingsHandler
would not be detected unless a DCHECK is made.

+    sources_.erase(it);
     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 {
     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_