Make ResourceFetcher return Resources with LoadError instead of nullptrs.

third_party/WebKit/Source/core/fetch/Resource.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) 2006 Samuel Weinig (sam.weinig@gmail.com)
     Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 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
@@ skipping 620 matching lines @@
 {
     if (isLoaded()) {
         c->notifyFinished(this);
         if (m_clients.contains(c)) {
             m_finishedClients.add(c);
             m_clients.remove(c);
         }
     }
 }
 
-static bool shouldSendCachedDataSynchronouslyForType(Resource::Type type)
+static bool typeNeedsSynchronousCacheHit(Resource::Type type)
 {
     // Some resources types default to return data synchronously.
     // For most of these, it's because there are layout tests that
     // expect data to return synchronously in case of cache hit. In
     // the case of fonts, there was a performance regression.
     // FIXME: Get to the point where we don't need to special-case sync/async
     // behavior for different resource types.
     if (type == Resource::Image)
         return true;
     if (type == Resource::CSSStyleSheet)
@@ skipping 29 matching lines @@
 
 void Resource::addClient(ResourceClient* client, PreloadReferencePolicy policy)
 {
     willAddClientOrObserver(policy);
 
     if (m_isRevalidating) {
         m_clients.add(client);
         return;
     }
 
-    // If we have existing data to send to the new client and the resource type supprts it, send it asynchronously.
-    if (!m_response.isNull() && !shouldSendCachedDataSynchronouslyForType(getType()) && !m_needsSynchronousCacheHit) {
+    // If an error has occurred or we have existing data to send to the new client and the resource type supprts it, send it asynchronously.
+    if ((errorOccurred() || !m_response.isNull()) && !typeNeedsSynchronousCacheHit(getType()) && !m_needsSynchronousCacheHit) {
         m_clientsAwaitingCallback.add(client);
         ResourceCallback::callbackHandler().schedule(this);
         return;
     }
 
     m_clients.add(client);
     didAddClient(client);
     return;
 }
 
@@ skipping 362 matching lines @@
     case Resource::TextTrack:
     case Resource::Media:
     case Resource::Manifest:
         return false;
     }
     NOTREACHED();
     return false;
 }
 
 } // namespace blink