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

Source/core/fetch/MemoryCache.cpp

Index: Source/core/fetch/MemoryCache.cpp
diff --git a/Source/core/fetch/MemoryCache.cpp b/Source/core/fetch/MemoryCache.cpp
index 4e0d6023a6601d46e792b103183c77e4eb2362d9..d2ac1a72337ac8ab2ea0a534f29aedfcead61172 100644
--- a/Source/core/fetch/MemoryCache.cpp
+++ b/Source/core/fetch/MemoryCache.cpp
@@ -223,10 +223,11 @@ void MemoryCache::pruneDeadResources()
         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->m_resource.get());
+                bool wasEvicted = evict(current->m_resource.get());
+                ASSERT_UNUSED(wasEvicted, wasEvicted);
             }
             current = previous;
         }
@@ -265,8 +266,10 @@ void MemoryCache::pruneDeadResources()
         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->m_resource.get());
+            if (!current->m_resource->hasClients() && !current->m_resource->isPreloaded()
+                && !current->m_resource->isCacheValidator() && current->m_resource->canDelete()) {
+                bool wasEvicted = evict(current->m_resource.get());
+                ASSERT_UNUSED(wasEvicted, wasEvicted);
                 if (targetSize && m_deadSize <= targetSize)
                     return;
             }