chrome: Cleanup class/struct forward declarations

chrome/browser/devtools/devtools_file_watcher.h

 // Copyright (c) 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_DEVTOOLS_DEVTOOLS_FILE_WATCHER_H_
 #define CHROME_BROWSER_DEVTOOLS_DEVTOOLS_FILE_WATCHER_H_
 
 #include <vector>
 
 #include "base/callback.h"
 #include "base/macros.h"
 
 namespace base {
 class FilePath;
-class FilePathWatcher;
 }
 
 class DevToolsFileWatcher {
  public:
   using WatchCallback = base::Callback<void(const std::vector<std::string>&,
                                             const std::vector<std::string>&,
                                             const std::vector<std::string>&)>;
   explicit DevToolsFileWatcher(const WatchCallback& callback);
   ~DevToolsFileWatcher();
 
   void AddWatch(const base::FilePath& path);
   void RemoveWatch(const base::FilePath& path);
 
  private:
   class SharedFileWatcher;
   static SharedFileWatcher* s_shared_watcher_;
 
   void InitSharedWatcher();
   void FileChanged(const base::FilePath&, int);
 
   scoped_refptr<SharedFileWatcher> shared_watcher_;
   WatchCallback callback_;
   DISALLOW_COPY_AND_ASSIGN(DevToolsFileWatcher);
 };
 
 #endif  // CHROME_BROWSER_DEVTOOLS_DEVTOOLS_FILE_WATCHER_H_