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
@@ skipping 647 matching lines @@
 void Resource::didAddClient(ResourceClient* c) {
   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)
     return true;
@@ skipping 31 matching lines @@
                          PreloadReferencePolicy policy) {
   CHECK(!m_isAddRemoveClientProhibited);
 
   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