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

extensions/renderer/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_NATIVE_HANDLER_H_
 #define EXTENSIONS_RENDERER_NATIVE_HANDLER_H_
 
 #include "base/basictypes.h"
 #include "v8/include/v8.h"
 
@@ skipping 11 matching lines @@
 
   // Create a new instance of the object this handler specifies.
   virtual v8::Handle<v8::Object> NewInstance() = 0;
 
   // Invalidate this object so it cannot be used any more. This is needed
   // because it's possible for this to outlive its owner context. Invalidate
   // must be called before this happens.
   //
   // Subclasses should override to invalidate their own V8 state. If they do
   // they must call their superclass' Invalidate().
+  //
+  // Invalidate() will be called on destruction, if it hasn't already been.
+  // Subclasses don't need to do it themselves.
   virtual void Invalidate();
 
  protected:
   // Allow subclasses to query valid state.
   bool is_valid() { return is_valid_; }
 
  private:
   bool is_valid_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeHandler);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_RENDERER_NATIVE_HANDLER_H_