Make MemoryCache::contains() take a const Resource pointer.

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 @@
         TypeStatistic xslStyleSheets;
         TypeStatistic fonts;
         TypeStatistic other;
     };
 
     Resource* resourceForURL(const KURL&);
 
     void add(Resource*);
     void replace(Resource* newResource, Resource* oldResource);
     void remove(Resource* resource) { evict(resource); }
-    bool contains(Resource*);
+    bool contains(const Resource*) const;
 
     static KURL removeFragmentIdentifierIfNeeded(const KURL& originalURL);
 
     // Sets the cache's memory capacities, in bytes. These will hold only approximately,
     // since the decoded cost of resources like scripts and stylesheets is not known.
     //  - minDeadBytes: The maximum number of bytes that dead resources should consume when the cache is under pressure.
     //  - maxDeadBytes: The maximum number of bytes that dead resources should consume when the cache is not under pressure.
     //  - totalBytes: The maximum number of bytes that the cache should consume overall.
     void setCapacities(size_t minDeadBytes, size_t maxDeadBytes, size_t totalBytes);
     void setDelayBeforeLiveDecodedPrune(double seconds) { m_delayBeforeLiveDecodedPrune = seconds; }
@@ skipping 91 matching lines @@
 
 // Returns the global cache.
 MemoryCache* memoryCache();
 
 // Sets the global cache, used to swap in a test instance.
 void setMemoryCacheForTesting(MemoryCache*);
 
 }
 
 #endif