REGRESSION(r157081): Fix multipart handling of ResourceFetcher

Source/core/fetch/ResourceFetcher.cpp

Index: Source/core/fetch/ResourceFetcher.cpp
diff --git a/Source/core/fetch/ResourceFetcher.cpp b/Source/core/fetch/ResourceFetcher.cpp
index 48ef9d71fca50d00a5308b29ee33d42409e5173d..d90fbdec68168b13bc0030d4d9e8faa4888ef188 100644
--- a/Source/core/fetch/ResourceFetcher.cpp
+++ b/Source/core/fetch/ResourceFetcher.cpp
@@ -1250,10 +1250,10 @@ void ResourceFetcher::didDownloadData(const Resource* resource, int dataLength,
 
 void ResourceFetcher::subresourceLoaderFinishedLoadingOnePart(ResourceLoader* loader)
 {
-    if (m_multipartLoaders)
-        m_multipartLoaders->add(loader);
-    if (m_loaders)
-        m_loaders->remove(loader);
+    if (!m_multipartLoaders)
+        m_multipartLoaders = adoptPtr(new ResourceLoaderSet());
+    m_multipartLoaders->add(loader);
+    m_loaders->remove(loader);
     if (LocalFrame* frame = this->frame())
         return frame->loader().checkLoadComplete(m_documentLoader);
 }
@@ -1270,9 +1270,10 @@ void ResourceFetcher::didInitializeResourceLoader(ResourceLoader* loader)
 
 void ResourceFetcher::willTerminateResourceLoader(ResourceLoader* loader)
 {
-    if (!m_loaders || !m_loaders->contains(loader))
-        return;
-    m_loaders->remove(loader);
+    if (m_loaders && m_loaders->contains(loader))
+        m_loaders->remove(loader);
+    if (m_multipartLoaders && m_multipartLoaders->contains(loader))
+        m_multipartLoaders->remove(loader);
     if (LocalFrame* frame = this->frame())
         frame->loader().checkLoadComplete(m_documentLoader);
 }