components: Cleanup class/struct fwd declarations

components/metrics/profiler/tracking_synchronizer_observer.h

 // 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 COMPONENTS_METRICS_PROFILER_TRACKING_SYNCHRONIZER_OBSERVER_H_
 #define COMPONENTS_METRICS_PROFILER_TRACKING_SYNCHRONIZER_OBSERVER_H_
 
 #include <vector>
 
 #include "base/macros.h"
 #include "base/process/process_handle.h"
 #include "base/time/time.h"
 #include "components/metrics/proto/chrome_user_metrics_extension.pb.h"
 
-namespace base {
-class TimeDelta;
-}
-
 namespace tracked_objects {
 struct ProcessDataPhaseSnapshot;
 }
 
 namespace metrics {
 
 // Set of profiling events, in no guaranteed order. Implemented as a vector
 // because we don't need to have an efficient .find() on it, so vector<> is more
 // efficient.
 typedef std::vector<ProfilerEventProto::ProfilerEvent> ProfilerEvents;
@@ skipping 50 matching lines @@
   TrackingSynchronizerObserver() {}
   virtual ~TrackingSynchronizerObserver() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TrackingSynchronizerObserver);
 };
 
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_PROFILER_TRACKING_SYNCHRONIZER_OBSERVER_H_