Implement the file chooser as a new resource "host"

ppapi/host/host_message_context.h

Index: ppapi/host/host_message_context.h
diff --git a/ppapi/host/host_message_context.h b/ppapi/host/host_message_context.h
new file mode 100644
index 0000000000000000000000000000000000000000..ea6c3018e1f59a06a3efb1ecc22fcc6d26570864
--- /dev/null
+++ b/ppapi/host/host_message_context.h
@@ -0,0 +1,28 @@
+// 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_COMMON_HOST_MESSAGE_CONTEXT_H_
+#define PPAPI_COMMON_HOST_MESSAGE_CONTEXT_H_
+
+#include "ipc/ipc_message.h"
+#include "ppapi/host/ppapi_host_export.h"
+#include "ppapi/proxy/resource_message_params.h"
+
+namespace ppapi {
+namespace host {
+
+struct PPAPI_HOST_EXPORT HostMessageContext {
+  HostMessageContext(const ppapi::proxy::ResourceMessageCallParams& cp)
+      : params(cp) {
+  }
+
+  const ppapi::proxy::ResourceMessageCallParams& params;
+
+  IPC::Message reply_msg;
+};
+
+}  // namespace host
+}  // namespace ppapi
+
+#endif  // PPAPI_COMMON_HOST_MESSAGE_CONTEXT_H_