[inspector] use own copy of third_party/inspector_protocol

third_party/inspector_protocol/lib/BackendCallback_h.template

+// Copyright (c) 2016 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 {{"_".join(config.protocol.namespace)}}_BackendCallback_h
+#define {{"_".join(config.protocol.namespace)}}_BackendCallback_h
+
+//#include "Forward.h"
+
+{% for namespace in config.protocol.namespace %}
+namespace {{namespace}} {
+{% endfor %}
+
+class {{config.lib.export_macro}} BackendCallback {
+public:
+    virtual ~BackendCallback() { }
+    virtual void sendFailure(const ErrorString&) = 0;
+};
+
+{% for namespace in config.protocol.namespace %}
+} // namespace {{namespace}}
+{% endfor %}
+
+#endif // !defined({{"_".join(config.protocol.namespace)}}_BackendCallback_h)