Fix empty href for favicon link element causing page to be fetched twice.

third_party/WebKit/Source/core/html/HTMLLinkElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights
  * reserved.
  * Copyright (C) 2009 Rob Buis (rwlbuis@gmail.com)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 306 matching lines @@
   // If the link element is not css, ignore it.
   if (equalIgnoringCase(getAttribute(typeAttr), "text/css")) {
     // FIXME: Add support for extracting links of sub-resources which
     // are inside style-sheet such as @import, @font-face, url(), etc.
     return hrefAttr;
   }
   return HTMLElement::subResourceAttributeName();
 }
 
 KURL HTMLLinkElement::href() const {
-  return document().completeURL(getAttribute(hrefAttr));
+  const String& url = getAttribute(hrefAttr);
+  if (url.isEmpty())
+    return KURL();
+  return document().completeURL(url);
 }
 
 const AtomicString& HTMLLinkElement::rel() const {
   return getAttribute(relAttr);
 }
 
 const AtomicString& HTMLLinkElement::type() const {
   return getAttribute(typeAttr);
 }
 
@@ skipping 22 matching lines @@
   LinkLoaderClient::trace(visitor);
   DOMTokenListObserver::trace(visitor);
 }
 
 DEFINE_TRACE_WRAPPERS(HTMLLinkElement) {
   visitor->traceWrappers(m_relList);
   HTMLElement::traceWrappers(visitor);
 }
 
 }  // namespace blink