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

ppapi/cpp/instance_handle.cc

Index: ppapi/cpp/instance_handle.cc
diff --git a/ppapi/cpp/instance_handle.cc b/ppapi/cpp/instance_handle.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8c3195a3b8c9e58051b8055f50c8d81d04d5e5bf
--- /dev/null
+++ b/ppapi/cpp/instance_handle.cc
@@ -0,0 +1,15 @@
+// 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.
+
+#include "ppapi/cpp/instance_handle.h"
+
+#include "ppapi/cpp/instance.h"
+
+namespace pp {
+
+InstanceHandle::InstanceHandle(Instance* instance)
+    : pp_instance_(instance->pp_instance()) {
+}
+
+}  // namespace pp