Add a warning whenever link preloads are not used

third_party/WebKit/Source/core/frame/LocalDOMWindow.h

Index: third_party/WebKit/Source/core/frame/LocalDOMWindow.h
diff --git a/third_party/WebKit/Source/core/frame/LocalDOMWindow.h b/third_party/WebKit/Source/core/frame/LocalDOMWindow.h
index 43e2d0e5fbef28264f5c607736074d374f1ceaf0..04c1ea594fc753cf83a6e75abacdccb2184950c0 100644
--- a/third_party/WebKit/Source/core/frame/LocalDOMWindow.h
+++ b/third_party/WebKit/Source/core/frame/LocalDOMWindow.h
@@ -224,6 +224,7 @@ private:
     // already LocalDOMWindow.
     bool isLocalDOMWindow() const override { return true; }
     bool isRemoteDOMWindow() const override { return false; }
+    void warnUnusedPreloads(TimerBase*);
 
     explicit LocalDOMWindow(LocalFrame&);
     void dispose();
@@ -236,6 +237,7 @@ private:
     Member<LocalFrame> m_frame;
     Member<Document> m_document;
     Member<DOMVisualViewport> m_visualViewport;
+    Timer<LocalDOMWindow> m_unusedPreloadsTimer;
 
     bool m_shouldPrintWhenFinishedLoading;