MemoryCache: make sure that Resources are evicted only when they can be deleted

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 215 matching lines @@
 
     size_t targetSize = static_cast<size_t>(capacity * cTargetPrunePercentage); // Cut by a percentage to avoid immediately pruning again.
 
     int size = m_allResources.size();
 
     // See if we have any purged resources we can evict.
     for (int i = 0; i < size; i++) {
         MemoryCacheEntry* current = m_allResources[i].m_tail;
         while (current) {
             MemoryCacheEntry* previous = current->m_previousInAllResourcesList;
-            if (current->m_resource->wasPurged()) {
+            if (current->m_resource->wasPurged() && current->m_resource->canDelete()) {
                 ASSERT(!current->m_resource->hasClients());
                 ASSERT(!current->m_resource->isPreloaded());
-                evict(current);
+                bool wasEvicted = evict(current);
+                ASSERT_UNUSED(wasEvicted, wasEvicted);
             }
             current = previous;
         }
     }
     if (targetSize && m_deadSize <= targetSize)
         return;
 
     bool canShrinkLRULists = true;
     for (int i = size - 1; i >= 0; i--) {
         // Remove from the tail, since this is the least frequently accessed of the objects.
@@ skipping 18 matching lines @@
             if (previous && !contains(previous->m_resource.get()))
                 break;
             current = previous;
         }
 
         // Now evict objects from this queue.
         current = m_allResources[i].m_tail;
         while (current) {
             MemoryCacheEntry* previous = current->m_previousInAllResourcesList;
             ASSERT(!previous || contains(previous->m_resource.get()));
-            if (!current->m_resource->hasClients() && !current->m_resource->isPreloaded() && !current->m_resource->isCacheValidator()) {
-                evict(current);
+            if (!current->m_resource->hasClients() && !current->m_resource->isPreloaded()
+                && !current->m_resource->isCacheValidator() && current->m_resource->canDelete()) {
+                bool wasEvicted = evict(current);
+                ASSERT_UNUSED(wasEvicted, wasEvicted);
                 if (targetSize && m_deadSize <= targetSize)
                     return;
             }
             if (previous && !contains(previous->m_resource.get()))
                 break;
             current = previous;
         }
 
         // Shrink the vector back down so we don't waste time inspecting
         // empty LRU lists on future prunes.
@@ skipping 391 matching lines @@
                 printf("(%.1fK, %.1fK, %uA, %dR, %d, %d); ", current->decodedSize() / 1024.0f, (current->encodedSize() + current->overheadSize()) / 1024.0f, current->accessCount(), current->hasClients(), current->isPurgeable(), current->wasPurged());
 
             current = prev;
         }
     }
 }
 
 #endif // MEMORY_CACHE_STATS
 
 } // namespace WebCore