New thunk system for Pepper proxy and implementation

ppapi/shared_impl/tracker_base.cc

+// Copyright (c) 2011 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/shared_impl/tracker_base.h"
+
+#include "base/logging.h"
+
+namespace ppapi {
+namespace shared_impl {
+
+static TrackerBase* (*g_global_getter)() = NULL;
+
+// static
+void TrackerBase::Init(TrackerBase* (*getter)()) {
+  g_global_getter = getter;
+}
+
+// static
+TrackerBase* TrackerBase::Get() {
+  return g_global_getter();
+}
+
+}  // namespace shared_impl
+}  // namespace ppapi