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

media/blink/url_index.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 MEDIA_BLINK_URL_INDEX_H_
 #define MEDIA_BLINK_URL_INDEX_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 213 matching lines @@
   friend class ResourceMultiBuffer;
   void RemoveUrlDataIfEmpty(const scoped_refptr<UrlData>& url_data);
 
   // Virtual so we can override it in tests.
   virtual scoped_refptr<UrlData> NewUrlData(const GURL& url,
                                             UrlData::CORSMode cors_mode);
 
   std::map<UrlData::KeyType, scoped_refptr<UrlData>> by_url_;
   blink::WebFrame* frame_;
   scoped_refptr<MultiBuffer::GlobalLRU> lru_;
-  bool prune_cb_active_;
 
   // log2 of block size in multibuffer cache. Defaults to kBlockSizeShift.
   // Currently only changed for testing purposes.
   const int block_shift_;
 
  protected:
   base::WeakPtrFactory<UrlIndex> weak_factory_;
 };
 
 }  // namespace media
 #endif  // MEDIA_BLINK_URL_INDEX_H_