Add a ScopedPPVar class for helping to track a reference to a base PP_Var.

ppapi/shared_impl/scoped_pp_var.cc

Index: ppapi/shared_impl/scoped_pp_var.cc
diff --git a/ppapi/shared_impl/scoped_pp_var.cc b/ppapi/shared_impl/scoped_pp_var.cc
new file mode 100644
index 0000000000000000000000000000000000000000..a91dbe6e488bdc5b7e83bf30988e1d98f503710a
--- /dev/null
+++ b/ppapi/shared_impl/scoped_pp_var.cc
@@ -0,0 +1,50 @@
+// 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/shared_impl/scoped_pp_var.h"
+
+#include "ppapi/shared_impl/ppapi_globals.h"
+#include "ppapi/shared_impl/var_tracker.h"
+
+namespace ppapi {
+
+namespace {
+
+void CallAddRef(const PP_Var& v) {
+  PpapiGlobals::Get()->GetVarTracker()->AddRefVar(v);
+}
+
+void CallRelease(const PP_Var& v) {
+  PpapiGlobals::Get()->GetVarTracker()->ReleaseVar(v);
+}
+
+}  // namespace
+
+ScopedPPVar::ScopedPPVar() : var_(PP_MakeUndefined()) {
+}
+
+ScopedPPVar::ScopedPPVar(const PP_Var& v) : var_(v) {
+  CallAddRef(var_);
+}
+
+ScopedPPVar::ScopedPPVar(const PassRef&, const PP_Var& v) : var_(v) {
+}
+
+ScopedPPVar::ScopedPPVar(const ScopedPPVar& other)
+    : var_(other.var_) {
+  CallAddRef(var_);
+}
+
+ScopedPPVar::~ScopedPPVar() {
+  CallRelease(var_);
+}
+
+ScopedPPVar& ScopedPPVar::operator=(const PP_Var& v) {
+  CallAddRef(v);
+  CallRelease(var_);
+  var_ = v;
+  return *this;
+}
+
+}  // namespace ppapi