Make `chrome` target build without unused data members on Linux.

extensions/browser/user_script_loader.h

 // Copyright 2014 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 EXTENSIONS_BROWSER_USER_SCRIPT_LOADER_H_
 #define EXTENSIONS_BROWSER_USER_SCRIPT_LOADER_H_
 
 #include <map>
 #include <set>
 
@@ skipping 147 matching lines @@
   std::set<HostID> changed_hosts_;
 
   // If the initial set of hosts has finished loading.
   bool ready_;
 
   // If list of user scripts is modified while we're loading it, we note
   // that we're currently mid-load and then start over again once the load
   // finishes.  This boolean tracks whether another load is pending.
   bool pending_load_;
 
-  // Whether or not we are currently loading.
-  bool is_loading_;
-
   // The browser_context for which the scripts managed here are installed.
   content::BrowserContext* browser_context_;
 
   // ID of the host that owns these scripts, if any. This is only set to a
   // non-empty value for declarative user script shared memory regions.
   HostID host_id_;
 
   // The associated observers.
   base::ObserverList<Observer> observers_;
 
   base::WeakPtrFactory<UserScriptLoader> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(UserScriptLoader);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_USER_SCRIPT_LOADER_H_