Handle main resource preload request better

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 656 matching lines @@
             m_resourceTimingReportTimer.startOneShot(0, FROM_HERE);
     }
 
     m_validatedURLs.add(request.resourceRequest().url());
 }
 
 ResourcePtr<Resource> ResourceFetcher::requestResource(Resource::Type type, FetchRequest& request)
 {
     ASSERT(request.options().synchronousPolicy == RequestAsynchronously || type == Resource::Raw);
 
+    // If loading main resource ensure main resources aren't preloaded.
+    if (type == Resource::MainResource && request.forPreload()) {

[Nate Chapin, 2014/06/06 23:00:01]

Ok. What if we move both this and the old code block to fetchMainResource()?
That address my organizational complaint, and avoids spinning up a
ResourceLoader unnecessarily.

+        return 0;
+    }
+
     TRACE_EVENT0("webkit", "ResourceFetcher::requestResource");
 
     KURL url = request.resourceRequest().url();
 
     WTF_LOG(ResourceLoading, "ResourceFetcher::requestResource '%s', charset '%s', priority=%d, forPreload=%u, type=%s", url.elidedString().latin1().data(), request.charset().latin1().data(), request.priority(), request.forPreload(), ResourceTypeName(type));
 
     // If only the fragment identifiers differ, it is the same resource.
     url = MemoryCache::removeFragmentIdentifierIfNeeded(url);
 
     if (!url.isValid())
@@ skipping 62 matching lines @@
                 memoryCache()->remove(resource.get());
             return request.options().synchronousPolicy == RequestSynchronously ? resource : 0;
         }
     }
 
     // FIXME: Temporarily leave main resource caching disabled for chromium,
     // see https://bugs.webkit.org/show_bug.cgi?id=107962. Before caching main
     // resources, we should be sure to understand the implications for memory
     // use.
     //
-    // Ensure main resources aren't preloaded, and other main resource loads
-    // are removed from cache to prevent reuse.
+    // Main resource loads are removed from cache to prevent reuse.
     if (type == Resource::MainResource) {
         ASSERT(policy != Use || m_documentLoader->substituteData().isValid());
         ASSERT(policy != Revalidate);
         memoryCache()->remove(resource.get());
-        if (request.forPreload())
-            return 0;
     }
 
     requestLoadStarted(resource.get(), request, policy == Use ? ResourceLoadingFromCache : ResourceLoadingFromNetwork);
 
     ASSERT(resource->url() == url.string());
     m_documentResources.set(resource->url(), resource);
     return resource;
 }
 
 void ResourceFetcher::resourceTimingReportTimerFired(Timer<ResourceFetcher>* timer)
@@ skipping 715 matching lines @@
     }
 }
 
 void ResourceFetcher::trace(Visitor* visitor)
 {
     visitor->trace(m_document);
     ResourceLoaderHost::trace(visitor);
 }
 
 }