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

ppapi/shared_impl/scoped_pp_var.h

Index: ppapi/shared_impl/scoped_pp_var.h
diff --git a/ppapi/shared_impl/scoped_pp_var.h b/ppapi/shared_impl/scoped_pp_var.h
new file mode 100644
index 0000000000000000000000000000000000000000..39ab2ecd7e5b6e770d8a5fc524f3bb3062e564eb
--- /dev/null
+++ b/ppapi/shared_impl/scoped_pp_var.h
@@ -0,0 +1,48 @@
+// 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_SHARED_IMPL_SCOPED_PP_VAR_H_
+#define PPAPI_SHARED_IMPL_SCOPED_PP_VAR_H_
+
+#include "ppapi/c/pp_var.h"
+#include "ppapi/shared_impl/ppapi_shared_export.h"
+
+namespace ppapi {
+
+class PPAPI_SHARED_EXPORT ScopedPPVar {
+ public:
+  struct PassRef {};
+
+  ScopedPPVar();
+
+  // Takes one reference to the given resource.
+  ScopedPPVar(const PP_Var& v);

[dmichael (off chromium), 2012/06/18 20:09:16]

probably should be explicit?

+
+  // Assumes responsibility for one ref that the var already has.
+  ScopedPPVar(const PassRef&, const PP_Var& v);
+
+  // Implicit copy constructor allowed.
+  ScopedPPVar(const ScopedPPVar& other);
+
+  ~ScopedPPVar();
+
+  ScopedPPVar& operator=(const PP_Var& r);
+  ScopedPPVar& operator=(const ScopedPPVar& other) {
+    return operator=(other.var_);
+  }
+
+  const PP_Var& get() const { return var_; }
+  operator PP_Var() const { return var_; }

[dmichael (off chromium), 2012/06/18 20:09:16]

This might be dangerous. Should we force people to think about whether or not
they're passing a reference by making them use get() explicitly when they aren't
passing a reference?

+
+  // Returns the PP_Var, passing the reference to the caller. This class
+  // will no longer hold the var.
+  PP_Var Release();
+
+ private:
+  PP_Var var_;
+};
+
+}  // namespace ppapi
+
+#endif  // PPAPI_SHARED_IMPL_SCOPED_PP_VAR_H_