Convert resources to take an instance key instead of an Instance*.

ppapi/cpp/pass_ref.h

+// Copyright (c) 2012 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 PPAPI_CPP_PASS_REF_H_
+#define PPAPI_CPP_PASS_REF_H_
+
+namespace pp {
+
+/// An annotation for constructors and other functions that take ownership of
+/// a pointer. For example, a resource constructor that takes ownership of a
+/// passed in PP_Resource ref count would take this to differentiate from
+/// the more typical use case of taking its own ref.
+enum PassRef { PASS_REF };
+
+}  // namespace pp
+
+#endif  // PPAPI_CPP_PASS_REF_H_