Add a warning whenever link preloads are not used

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

Index: third_party/WebKit/Source/core/fetch/ResourceFetcher.h
diff --git a/third_party/WebKit/Source/core/fetch/ResourceFetcher.h b/third_party/WebKit/Source/core/fetch/ResourceFetcher.h
index 847ce9e077d904310327c9ab0cf57a979bcff074..e1bcb9bb3a32a17f8f538bccb1c8e038d77d34d0 100644
--- a/third_party/WebKit/Source/core/fetch/ResourceFetcher.h
+++ b/third_party/WebKit/Source/core/fetch/ResourceFetcher.h
@@ -96,9 +96,11 @@ public:
 
     bool isPreloaded(const KURL&) const;
     int countPreloads() const { return m_preloads ? m_preloads->size() : 0; }
+    bool hasUnusedLinkPreloads() { return m_unusedLinkPreloadCounter > 0; }
     void clearPreloads(ClearPreloadsPolicy = ClearAllPreloads);
     void preloadStarted(Resource*);
     void logPreloadStats();
+    void warnUnusedPreloads();
 
     MHTMLArchive* archive() const { return m_archive.get(); }
     ArchiveResource* createArchive(Resource*);
@@ -180,6 +182,7 @@ private:
     mutable DocumentResourceMap m_documentResources;
 
     Member<HeapListHashSet<Member<Resource>>> m_preloads;
+    unsigned m_unusedLinkPreloadCounter;
     Member<MHTMLArchive> m_archive;
 
     Timer<ResourceFetcher> m_resourceTimingReportTimer;