diff -r 000000000000 -r 6474c204b198 dom/plugins/ipc/PluginIdentifierParent.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/plugins/ipc/PluginIdentifierParent.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,75 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=2 et :
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "PluginIdentifierParent.h"
+
+#include "nsNPAPIPlugin.h"
+#include "nsServiceManagerUtils.h"
+#include "PluginScriptableObjectUtils.h"
+#include "nsCxPusher.h"
+#include "mozilla/unused.h"
+
+using namespace mozilla::plugins::parent;
+
+namespace mozilla {
+namespace plugins {
+
+bool
+PluginIdentifierParent::RecvRetain()
+{
+  mTemporaryRefs = 0;
+
+  // Intern the jsid if necessary.
+  AutoSafeJSContext cx;
+  JS::Rooted<jsid> id(cx, NPIdentifierToJSId(mIdentifier));
+  if (JSID_IS_INT(id)) {
+    return true;
+  }
+
+  // The following is what nsNPAPIPlugin.cpp does. Gross, but the API doesn't
+  // give you a NPP to play with.
+  JS::Rooted<JSString*> str(cx, JSID_TO_STRING(id));
+  JSString* str2 = JS_InternJSString(cx, str);
+  if (!str2) {
+    return false;
+  }
+
+  NS_ASSERTION(str == str2, "Interning a string in a JSID should always return the same string.");
+
+  return true;
+}
+
+PluginIdentifierParent::StackIdentifier::StackIdentifier
+    (PluginInstanceParent* inst, NPIdentifier aIdentifier)
+  : mIdentifier(inst->Module()->GetIdentifierForNPIdentifier(inst->GetNPP(), aIdentifier))
+{
+}
+
+PluginIdentifierParent::StackIdentifier::StackIdentifier
+    (NPObject* aObject, NPIdentifier aIdentifier)
+  : mIdentifier(nullptr)
+{
+  PluginInstanceParent* inst = GetInstance(aObject);
+  mIdentifier = inst->Module()->GetIdentifierForNPIdentifier(inst->GetNPP(), aIdentifier);
+}
+
+PluginIdentifierParent::StackIdentifier::~StackIdentifier()
+{
+  if (!mIdentifier) {
+    return;
+  }
+
+  if (!mIdentifier->IsTemporary()) {
+    return;
+  }
+
+  if (mIdentifier->RemoveTemporaryRef()) {
+    unused << PPluginIdentifierParent::Send__delete__(mIdentifier);
+  }
+}
+
+} // namespace mozilla::plugins
+} // namespace mozilla