Cloning a bunch of stuff from the native_client repository at r6528

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

Index: ppapi/native_client/src/shared/ppapi_proxy/proxy_var.h
===================================================================
--- ppapi/native_client/src/shared/ppapi_proxy/proxy_var.h	(revision 0)
+++ ppapi/native_client/src/shared/ppapi_proxy/proxy_var.h	(revision 0)
@@ -0,0 +1,56 @@
+// 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.
+
+#ifndef NATIVE_CLIENT_SRC_SHARED_PPAPI_PROXY_PROXY_VAR_H_
+#define NATIVE_CLIENT_SRC_SHARED_PPAPI_PROXY_PROXY_VAR_H_
+
+#include "native_client/src/include/nacl_macros.h"
+#include "native_client/src/include/nacl_memory.h"
+#include "native_client/src/include/ref_counted.h"
+#include "ppapi/c/pp_var.h"
+
+namespace ppapi_proxy {
+
+// Complex PP_Var types (such as strings) have a copy of the variant's contents
+// cached by the proxy.  This is done so that PP_Vars can be reference counted,
+// and their contents accessed "locally" by NaCl modules without having to
+// perform a complete round trip to the browser for each such operation.
+//
+// Note: this class is intended to be sub-classed to handle specific content
+// types such as strings, dictionaries, or arrays.
+class ProxyVar : public nacl::RefCounted<ProxyVar> {
+ public:
+  // The type of this cached object.  Simple types (int, bool, etc.) are not
+  // cached.
+  PP_VarType pp_var_type() const { return pp_var_type_; }
+
+  // The assigned unique id associated with this object.  Use this as the id
+  // for the corresponding PP_Var.
+  int64_t id() const { return id_; }
+
+ protected:
+  // Initialize this instance to represent a PP_Var of type |pp_var_type|.
+  // Generates a unique id for this instance, and sets the reference count to 1.
+  // Subclasses should implement ctors that handle specific content data.
+  explicit ProxyVar(PP_VarType pp_var_type);
+
+  virtual ~ProxyVar() {}
+
+ private:
+  friend class nacl::RefCounted<ProxyVar>;
+  PP_VarType pp_var_type_;
+  int64_t id_;
+
+  ProxyVar();  // Not implemented - do not use.
+  NACL_DISALLOW_COPY_AND_ASSIGN(ProxyVar);
+
+  // A counter for unique ids.
+  static int64_t unique_var_id;
+};
+
+typedef scoped_refptr<ProxyVar> SharedProxyVar;
+
+}  // namespace ppapi_proxy
+
+#endif  // NATIVE_CLIENT_SRC_SHARED_PPAPI_PROXY_PROXY_VAR_H_