[Extensions Bindings] Notify of event unregistration on invalidation

extensions/renderer/api_event_handler.h

 // Copyright 2016 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_API_EVENT_HANDLER_H_
 #define EXTENSIONS_RENDERER_API_EVENT_HANDLER_H_
 
 #include <string>
 
 #include "base/callback.h"
@@ skipping 39 matching lines @@
   // being dispatched to the event, and the function to dispatch the event to
   // listeners.
   void RegisterArgumentMassager(v8::Local<v8::Context> context,
                                 const std::string& event_name,
                                 v8::Local<v8::Function> function);
 
   // Returns the EventListeners for a given |event_name| and |context|.
   size_t GetNumEventListenersForTesting(const std::string& event_name,
                                         v8::Local<v8::Context> context);
 
+  // Invalidates listeners for the given |context|. It's a shame we have to
+  // have this separately (as opposed to hooking into e.g. a PerContextData
+  // destructor), but we need to do this before the context is fully removed
+  // (because the associated extension ScriptContext needs to be valid).
+  void InvalidateContext(v8::Local<v8::Context> context);
+
  private:
   // Method to run a given v8::Function. Curried in for testing.
   binding::RunJSFunction call_js_;
 
   EventListenersChangedMethod listeners_changed_;
 
   DISALLOW_COPY_AND_ASSIGN(APIEventHandler);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_RENDERER_API_EVENT_HANDLER_H_