Cloning a bunch of stuff from the native_client repository at r6528

ppapi/native_client/src/shared/ppapi_proxy/proxy_var.cc

+// Copyright (c) 2011 The Native Client 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 "native_client/src/shared/ppapi_proxy/proxy_var.h"
+
+#include "native_client/src/shared/platform/nacl_sync_checked.h"
+#include "native_client/src/untrusted/pthread/pthread.h"
+
+#include <limits>
+
+namespace ppapi_proxy {
+
+namespace {
+
+pthread_mutex_t mu = PTHREAD_MUTEX_INITIALIZER;
+
+}  // namespace
+
+int64_t ProxyVar::unique_var_id = 0;
+
+ProxyVar::ProxyVar(PP_VarType pp_var_type) : pp_var_type_(pp_var_type) {
+  // Roll id of INT64_MAX to 1, because an id of 0 is not valid.
+  nacl::ScopedPthreadMutexLock ml(&mu);
+  if (unique_var_id > std::numeric_limits<int64_t>::max() - 1)
+    unique_var_id = 0;
+  id_ = ++unique_var_id;
+}
+
+}  // namespace ppapi_proxy