chrome: Cleanup class/struct forward declarations

chrome/browser/android/metrics/uma_session_stats.h

 // Copyright 2015 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 CHROME_BROWSER_ANDROID_METRICS_UMA_SESSION_STATS_H_
 #define CHROME_BROWSER_ANDROID_METRICS_UMA_SESSION_STATS_H_
 
 #include <jni.h>
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/android/scoped_java_ref.h"
 #include "base/macros.h"
 #include "base/time/time.h"
 
-class UserActionRateCounter;
-
 // The native part of java UmaSessionStats class.
 class UmaSessionStats {
  public:
   UmaSessionStats();
 
   void UmaResumeSession(JNIEnv* env,
                         const base::android::JavaParamRef<jobject>& obj);
   void UmaEndSession(JNIEnv* env,
                      const base::android::JavaParamRef<jobject>& obj);
 
@@ skipping 11 matching lines @@
   base::TimeTicks session_start_time_;
   int active_session_count_;
 
   DISALLOW_COPY_AND_ASSIGN(UmaSessionStats);
 };
 
 // Registers the native methods through jni
 bool RegisterUmaSessionStats(JNIEnv* env);
 
 #endif  // CHROME_BROWSER_ANDROID_METRICS_UMA_SESSION_STATS_H_