Revert of Move the event attach/detach logic on unload from event.js to

extensions/renderer/object_backed_native_handler.h

 // Copyright 2014 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 EXTENSIONS_RENDERER_OBJECT_BACKED_NATIVE_HANDLER_H_
 #define EXTENSIONS_RENDERER_OBJECT_BACKED_NATIVE_HANDLER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 20 matching lines @@
 
   v8::Isolate* GetIsolate() const;
 
  protected:
   typedef base::Callback<void(const v8::FunctionCallbackInfo<v8::Value>&)>
       HandlerFunction;
 
   // Installs a new 'route' from |name| to |handler_function|. This means that
   // NewInstance()s of this ObjectBackedNativeHandler will have a property
   // |name| which will be handled by |handler_function|.
-  //
-  // Routed functions are destroyed along with the destruction of this class,
-  // and are never called back into, therefore it's safe for |handler_function|
-  // to bind to base::Unretained.
   void RouteFunction(const std::string& name,
                      const HandlerFunction& handler_function);
 
   ScriptContext* context() const { return context_; }
 
   void Invalidate() override;
 
  private:
   // Callback for RouteFunction which routes the V8 call to the correct
   // base::Bound callback.
@@ skipping 18 matching lines @@
   ScriptContext* context_;
 
   v8::Global<v8::ObjectTemplate> object_template_;
 
   DISALLOW_COPY_AND_ASSIGN(ObjectBackedNativeHandler);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_RENDERER_OBJECT_BACKED_NATIVE_HANDLER_H_