[Extensions Bindings] Notify of event unregistration on invalidation

extensions/renderer/native_extension_bindings_system.cc

 // 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.
 
 #include "extensions/renderer/native_extension_bindings_system.h"
 
 #include "base/command_line.h"
 #include "base/memory/ptr_util.h"
 #include "content/public/common/content_switches.h"
 #include "extensions/common/constants.h"
@@ skipping 350 matching lines @@
   }
 
   // Note: it's a shame we can't delay this (until, say, we knew an API would
   // actually be used), but it's needed for some of our crazier hooks, like
   // web/guest view.
   context->module_system()->SetGetInternalAPIHook(
       get_internal_api_.Get(isolate));
 }
 
 void NativeExtensionBindingsSystem::WillReleaseScriptContext(
-    ScriptContext* context) {}
+    ScriptContext* context) {
+  v8::HandleScope handle_scope(context->isolate());
+  api_system_.WillReleaseContext(context->v8_context());
+}
 
 void NativeExtensionBindingsSystem::UpdateBindingsForContext(
     ScriptContext* context) {
   v8::HandleScope handle_scope(context->isolate());
   v8::Local<v8::Context> v8_context = context->v8_context();
   v8::Local<v8::Object> chrome = GetOrCreateChrome(v8_context);
   if (chrome.IsEmpty())
     return;
 
   BindingsSystemPerContextData* data = GetBindingsDataFromContext(v8_context);
@@ skipping 242 matching lines @@
 
 void NativeExtensionBindingsSystem::OnEventListenerChanged(
     const std::string& event_name,
     binding::EventListenersChanged change,
     v8::Local<v8::Context> context) {
   send_event_listener_ipc_.Run(
       change, ScriptContextSet::GetContextByV8Context(context), event_name);
 }
 
 }  // namespace extensions