Add a warning whenever link preloads are not used

third_party/WebKit/Source/core/fetch/ResourceFetcher.h

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller <mueller@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
     version 2 of the License, or (at your option) any later version.
@@ skipping 78 matching lines @@
     FetchContext& context() const { return m_context ? *m_context.get() : FetchContext::nullInstance(); }
     void clearContext();
 
     int requestCount() const;
     bool hasPendingRequest() const;
 
     enum ClearPreloadsPolicy { ClearAllPreloads, ClearSpeculativeMarkupPreloads };
 
     bool isPreloaded(const KURL&) const;
     int countPreloads() const { return m_preloads ? m_preloads->size() : 0; }
+    bool isUnusedLinkPreloads() { return m_linkPreloadCounter > 0; }

[Charlie Harrison, 2016/09/14 21:07:59]

hasUnusedLinkPreloads?

     void clearPreloads(ClearPreloadsPolicy = ClearAllPreloads);
     void preloadStarted(Resource*);
     void logPreloadStats();
+    void warnUnusedPreloads();
 
     MHTMLArchive* archive() const { return m_archive.get(); }
     ArchiveResource* createArchive(Resource*);
 
     void setDefersLoading(bool);
     void stopFetching();
     bool isFetching() const;
 
     bool willFollowRedirect(Resource*, ResourceRequest&, const ResourceResponse&, int64_t encodedDataLength);
     enum DidFinishLoadingReason {
@@ skipping 61 matching lines @@
     void reloadImagesIfNotDeferred();
 
     void updateMemoryCacheStats(Resource*, RevalidationPolicy, const FetchRequest&,  const ResourceFactory&, bool isStaticData) const;
 
     Member<FetchContext> m_context;
 
     HashSet<String> m_validatedURLs;
     mutable DocumentResourceMap m_documentResources;
 
     Member<HeapListHashSet<Member<Resource>>> m_preloads;
+    unsigned m_linkPreloadCounter;

[Charlie Harrison, 2016/09/14 21:07:59]

m_unusedLinkPreloadCounter?

     Member<MHTMLArchive> m_archive;
 
     Timer<ResourceFetcher> m_resourceTimingReportTimer;
 
     using ResourceTimingInfoMap = HeapHashMap<Member<Resource>, std::unique_ptr<ResourceTimingInfo>>;
     ResourceTimingInfoMap m_resourceTimingInfoMap;
 
     Vector<std::unique_ptr<ResourceTimingInfo>> m_scheduledResourceTimingReports;
 
     HeapHashSet<Member<ResourceLoader>> m_loaders;
@@ skipping 41 matching lines @@
             m_loader->m_allowStaleResources = m_previousState;
     }
 private:
     Member<ResourceFetcher> m_loader;
     bool m_previousState;
 };
 
 } // namespace blink
 
 #endif // ResourceFetcher_h