Teach WebURLRequest about Fetch's "frame type" concept.

Source/core/fetch/ResourceFetcher.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) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
     Copyright (C) 2009 Torch Mobile Inc. http://www.torchmobile.com/
 
     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 358 matching lines @@
 }
 
 ResourcePtr<RawResource> ResourceFetcher::fetchRawResource(FetchRequest& request)
 {
     ASSERT(request.resourceRequest().requestContext() != WebURLRequest::RequestContextUnspecified);
     return toRawResource(requestResource(Resource::Raw, request));
 }
 
 ResourcePtr<RawResource> ResourceFetcher::fetchMainResource(FetchRequest& request, const SubstituteData& substituteData)
 {
+    ASSERT(request.resourceRequest().frameType() != WebURLRequest::FrameTypeNone);
     if (substituteData.isValid())
         preCacheSubstituteDataForMainResource(request, substituteData);
     return toRawResource(requestResource(Resource::MainResource, request));
 }
 
 ResourcePtr<RawResource> ResourceFetcher::fetchMedia(FetchRequest& request)
 {
     return toRawResource(requestResource(Resource::Media, request));
 }
 
@@ skipping 1133 matching lines @@
     }
 }
 
 void ResourceFetcher::trace(Visitor* visitor)
 {
     visitor->trace(m_document);
     ResourceLoaderHost::trace(visitor);
 }
 
 }