Create a PPAPI host for new resource message routing.

ppapi/host/resource_host.h

Index: ppapi/host/resource_host.h
diff --git a/ppapi/host/resource_host.h b/ppapi/host/resource_host.h
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+// 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_HOST_RESOURCE_HOST_H_
+#define PPAPI_HOST_RESOURCE_HOST_H_
+
+#include "base/basictypes.h"
+#include "ppapi/c/pp_resource.h"
+#include "ppapi/host/ppapi_host_export.h"
+#include "ppapi/shared_impl/host_resource.h"
+
+namespace IPC {
+class Message;
+}
+
+namespace ppapi {
+namespace host {
+
+struct HostMessageContext;
+class PpapiHost;
+
+// Some (but not all) resources have a corresponding object in the host side
+// that is kept alive as long as the resource in the plugin is alive. This is
+// the base class for such objects.
+class PPAPI_HOST_EXPORT ResourceHost {
+ public:
+  ResourceHost(PpapiHost* host, PP_Instance instance, PP_Resource resource);
+  virtual ~ResourceHost();
+
+  PpapiHost* host() { return host_; }
+  PP_Instance pp_instance() const { return pp_instance_; }
+  PP_Resource pp_resource() const { return pp_resource_; }
+
+  // Handles messages associated with a given resource object. If the flags
+  // indicate that a response is required, the return value of this function
+  // will be sent as a resource message "response" along with the message
+  // specified in the reply of the context.
+  //
+  // You can do a response asynchronously by returning PP_OK_COMPLETIONPENDING.
+  // This will cause the reply to be skipped, and the class implementing this
+  // function will take responsibility for issuing the callback later.
+  //
+  // If you don't have a particular reply message, you can just ignore
+  // the reply in the message context. However, if you have a reply more than
+  // just the int32_t result code, set the reply to be the message of your
+  // choosing.
+  //
+  // The default implementation just returns PP_ERROR_NOTSUPPORTED.
+  virtual int32_t OnResourceMessageReceived(const IPC::Message& msg,
+                                            HostMessageContext* context);
+
+ private:
+  // The host that owns this object.
+  PpapiHost* host_;
+
+  PP_Instance pp_instance_;
+  PP_Resource pp_resource_;
+
+  DISALLOW_COPY_AND_ASSIGN(ResourceHost);
+};
+
+}  // namespace host
+}  // namespace ppapi
+
+#endif  // PPAPI_HOST_RESOURCE_HOST_H_