MemoryCache::resourceForURL(): add argument validation.

Source/core/fetch/MemoryCache.cpp

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@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 191 matching lines @@
 }
 
 Resource* MemoryCache::resourceForURL(const KURL& resourceURL)
 {
     return resourceForURL(resourceURL, defaultCacheIdentifier());
 }
 
 Resource* MemoryCache::resourceForURL(const KURL& resourceURL, const String& cacheIdentifier)
 {
     ASSERT(WTF::isMainThread());
+    if (!resourceURL.isValid() || resourceURL.isNull())
+        return nullptr;
+    ASSERT(!cacheIdentifier.isNull());
     ResourceMap* resources = m_resourceMaps.get(cacheIdentifier);
     if (!resources)
         return nullptr;
     KURL url = removeFragmentIdentifierIfNeeded(resourceURL);
     MemoryCacheEntry* entry = resources->get(url);
     if (!entry)
         return nullptr;
     Resource* resource = entry->m_resource.get();
     if (resource && !resource->lock()) {
         ASSERT(!resource->hasClients());
@@ skipping 626 matching lines @@
                 printf("(%.1fK, %.1fK, %uA, %dR, %d, %d); ", currentResource->decodedSize() / 1024.0f, (currentResource->encodedSize() + currentResource->overheadSize()) / 1024.0f, current->m_accessCount, currentResource->hasClients(), currentResource->isPurgeable(), currentResource->wasPurged());
 
             current = current->m_previousInAllResourcesList;
         }
     }
 }
 
 #endif // MEMORY_CACHE_STATS
 
 } // namespace blink