chrome: Cleanup class/struct forward declarations

chrome/browser/extensions/activity_log/activity_log_policy.h

 // Copyright 2013 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_EXTENSIONS_ACTIVITY_LOG_ACTIVITY_LOG_POLICY_H_
 #define CHROME_BROWSER_EXTENSIONS_ACTIVITY_LOG_ACTIVITY_LOG_POLICY_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 10 matching lines @@
 #include "chrome/browser/extensions/activity_log/activity_actions.h"
 #include "chrome/browser/extensions/activity_log/activity_database.h"
 #include "chrome/common/extensions/api/activity_log_private.h"
 #include "content/public/browser/browser_thread.h"
 #include "url/gurl.h"
 
 class Profile;
 class GURL;
 
 namespace base {
+class Clock;
 class FilePath;
 }
 
 namespace extensions {
 
-class Extension;
 
 // An abstract class for processing and summarizing activity log data.
 // Subclasses will generally store data in an SQLite database (the
 // ActivityLogDatabasePolicy subclass includes some helper methods to assist
 // with this case), but this is not absolutely required.
 //
 // Implementations should support:
 // (1) Receiving Actions to process, and summarizing, compression, and storing
 //     these as appropriate.
 // (2) Reading Actions back from storage.
@@ skipping 179 matching lines @@
  private:
   // See the comments for the ActivityDatabase class for a discussion of how
   // database cleanup runs.
   ActivityDatabase* db_;
   base::FilePath database_path_;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_ACTIVITY_LOG_ACTIVITY_LOG_POLICY_H_