[tracing] Support BACKGROUND mode in MemoryCache dump provider

third_party/WebKit/Source/core/fetch/MemoryCache.h

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller <mueller@kde.org>
     Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
 
     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Library General Public
     License as published by the Free Software Foundation; either
     version 2 of the License, or (at your option) any later version.
 
@@ skipping 119 matching lines @@
     ~MemoryCache();
     DECLARE_TRACE();
 
     struct TypeStatistic {
         STACK_ALLOCATED();
         size_t count;
         size_t size;
         size_t liveSize;
         size_t decodedSize;
         size_t encodedSize;
+        size_t overheadSize;
         size_t encodedSizeDuplicatedInDataURLs;
 
         TypeStatistic()
             : count(0)
             , size(0)
             , liveSize(0)
             , decodedSize(0)
             , encodedSize(0)
+            , overheadSize(0)
             , encodedSizeDuplicatedInDataURLs(0)
         {
         }
 
         void addResource(Resource*);
     };
 
     struct Statistics {
         STACK_ALLOCATED();
         TypeStatistic images;
@@ skipping 136 matching lines @@
 // Returns the global cache.
 CORE_EXPORT MemoryCache* memoryCache();
 
 // Sets the global cache, used to swap in a test instance. Returns the old
 // MemoryCache object.
 CORE_EXPORT MemoryCache* replaceMemoryCacheForTesting(MemoryCache*);
 
 } // namespace blink
 
 #endif