[PPAPI] Added a new Var subclass, ResourceVar.

ppapi/shared_impl/resource_var.h

+// Copyright 2013 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_RESOURCE_VAR_H_
+#define PPAPI_SHARED_IMPL_RESOURCE_VAR_H_
+
+#include "ipc/ipc_message.h"

[Matt Giuca, 2013/08/28 07:12:14]

Note: This violates a deps rule (shared_impl can't depend upon ipc). I hope to
get this rule changed (see https://codereview.chromium.org/23532006/), but if
not, we'll have to forward-declare IPC::Message, and make it a scoped_ptr.

+#include "ppapi/c/pp_resource.h"
+#include "ppapi/c/pp_var.h"
+#include "ppapi/shared_impl/ppapi_shared_export.h"
+#include "ppapi/shared_impl/var.h"
+
+namespace ppapi {
+
+// Represents a resource Var.
+class PPAPI_SHARED_EXPORT ResourceVar : public Var {
+ public:
+  ResourceVar();  // Makes a null resource var.
+  ResourceVar(PP_Resource resource_id);
+  virtual ~ResourceVar();
+
+  // Gets the resource ID associated with this var.
+  // This is 0 if a resource is still pending.
+  PP_Resource resource_id() const { return resource_id_; }
+
+  // Gets the message for creating a plugin-side resource.
+  // May be an empty message.
+  const IPC::Message& creation_message() const { return creation_message_; }
+
+  // Var override.
+  virtual ResourceVar* AsResourceVar() OVERRIDE;
+  virtual PP_VarType GetType() const OVERRIDE;
+
+  // Helper function that converts a PP_Var to a ResourceVar. This will
+  // return NULL if the PP_Var is not of Resource type.
+  static ResourceVar* FromPPVar(PP_Var var);
+
+ private:
+  // Real resource ID in the plugin. 0 if one has not yet been created
+  // (indicating that there is a pending host resource).
+  PP_Resource resource_id_;
+
+  // If the plugin-side resource has not yet been created, carries a message to
+  // create a resource of the specific type on the plugin side.
+  // Otherwise, carries an empty message.
+  IPC::Message creation_message_;
+
+  DISALLOW_COPY_AND_ASSIGN(ResourceVar);
+};
+
+}  // namespace ppapi
+
+#endif  // PPAPI_SHARED_IMPL_RESOURCE_VAR_H_