Make multipart image documents work again.

Source/core/loader/DocumentLoader.cpp

Index: Source/core/loader/DocumentLoader.cpp
diff --git a/Source/core/loader/DocumentLoader.cpp b/Source/core/loader/DocumentLoader.cpp
index f0e05a4a196f2da91bb9dcdc043b57990dab9cf2..d80bd429baa7451381f37619dd4842c2e7ad9369 100644
--- a/Source/core/loader/DocumentLoader.cpp
+++ b/Source/core/loader/DocumentLoader.cpp
@@ -543,6 +543,11 @@ void DocumentLoader::appendRedirect(const KURL& url)
     m_redirectChain.append(url);
 }
 
+bool DocumentLoader::loadingMultipartContent() const
+{
+    return mainResourceLoader() ? mainResourceLoader()->loadingMultipartContent() : false;
+}
+
 void DocumentLoader::detachFromFrame()
 {
     ASSERT(m_frame);