Keep only base/extractor.[cc|h].

tools/OmahaCompatibility/common/ping_observer.h

-// Copyright 2008-2009 Google Inc.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-// ========================================================================
-
-#ifndef OMAHA_TOOLS_SRC_OMAHACOMPATIBILITY_COMMON_PING_OBSERVER_H_
-#define OMAHA_TOOLS_SRC_OMAHACOMPATIBILITY_COMMON_PING_OBSERVER_H_
-
-#include "omaha/worker/app_request_data.h"
-
-namespace omaha {
-
-// Interface for receiving ping events from the http server.
-class PingObserver {
- public:
-  virtual ~PingObserver() {}
-  virtual void Observe(const AppRequestData& data) = 0;
-};
-
-}  // namespace omaha
-
-#endif  // OMAHA_TOOLS_SRC_OMAHACOMPATIBILITY_COMMON_PING_OBSERVER_H_