Remove unneeded includes of base/string_piece.h

chrome/browser/extensions/user_script_master.h

 // Copyright (c) 2008 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_USER_SCRIPT_MASTER_H_
 #define CHROME_BROWSER_EXTENSIONS_USER_SCRIPT_MASTER_H_
 
 #include <vector>
 
 #include "base/directory_watcher.h"
 #include "base/file_path.h"
 #include "base/message_loop.h"
 #include "base/process.h"
 #include "base/scoped_ptr.h"
 #include "base/shared_memory.h"
-#include "base/string_piece.h"
 #include "chrome/common/extensions/user_script.h"
 #include "googleurl/src/gurl.h"
 #include "testing/gtest/include/gtest/gtest_prod.h"
 
+class StringPiece;
+
 // Manages a segment of shared memory that contains the user scripts the user
 // has installed.  Lives on the UI thread.
 class UserScriptMaster : public base::RefCounted<UserScriptMaster>,
                          public DirectoryWatcher::Delegate {
  public:
   // For testability, the constructor takes the MessageLoop to run the
   // script-reloading worker on as well as the path the scripts live in.
   // These are normally the file thread and a directory inside the profile.
   UserScriptMaster(MessageLoop* worker, const FilePath& script_dir);
   ~UserScriptMaster();
@@ skipping 116 matching lines @@
 
   // If the script directory is modified while we're rescanning it, we note
   // that we're currently mid-scan and then start over again once the scan
   // finishes.  This boolean tracks whether another scan is pending.
   bool pending_scan_;
 
   DISALLOW_COPY_AND_ASSIGN(UserScriptMaster);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_USER_SCRIPT_MASTER_H_