Fix null dereference on MemoryCache.

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

Index: third_party/WebKit/Source/core/fetch/MemoryCache.cpp
diff --git a/third_party/WebKit/Source/core/fetch/MemoryCache.cpp b/third_party/WebKit/Source/core/fetch/MemoryCache.cpp
index c609a0ed06545b483c4f22cac70d5e2febe69b98..0aad6d242b1ed8e5bb127511a4c0bb39f1e9fc7c 100644
--- a/third_party/WebKit/Source/core/fetch/MemoryCache.cpp
+++ b/third_party/WebKit/Source/core/fetch/MemoryCache.cpp
@@ -354,7 +354,7 @@ void MemoryCache::pruneDeadResources(PruneStrategy strategy)
             }
             // Decoded data may reference other resources. Stop iterating if 'previous' somehow got
             // kicked out of cache during destroyDecodedData().
-            if (previous && !contains(previous->m_resource.get()))
+            if (!previous || !previous->m_resource || !contains(previous->m_resource.get()))
                 break;
             current = previous;
         }
@@ -374,7 +374,7 @@ void MemoryCache::pruneDeadResources(PruneStrategy strategy)
                 if (targetSize && m_deadSize <= targetSize)
                     return;
             }
-            if (previous && !contains(previous->m_resource.get()))
+            if (!previous || !previous->m_resource || !contains(previous->m_resource.get()))
                 break;
             current = previous;
         }
@@ -793,6 +793,15 @@ void MemoryCache::onMemoryDump(WebMemoryDumpLevelOfDetail levelOfDetail, WebProc
     }
 }
 
+bool MemoryCache::isInSameLRUListForTest(const Resource* x, const Resource* y)
+{
+    MemoryCacheEntry* ex = getEntryForResource(x);
+    MemoryCacheEntry* ey = getEntryForResource(y);
+    ASSERT(ex);
+    ASSERT(ey);
+    return lruListFor(ex->m_accessCount, x->size()) == lruListFor(ey->m_accessCount, y->size());
+}
+
 void MemoryCache::registerLiveResource(Resource& resource)
 {
 #if ENABLE(OILPAN)