Correct UseCounter::FormNameAccessForImageElement.

third_party/WebKit/Source/core/html/HTMLFormElement.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) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.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 818 matching lines @@
         if (elements.isEmpty())
             return;
     }
 
     // Second call may return different results from the first call,
     // but if the first the size cannot be zero.
     WillBeHeapVector<RefPtrWillBeMember<Element>> elements;
     getNamedElements(name, elements);
     ASSERT(!elements.isEmpty());
 
+    bool onlyMatchImg = !elements.isEmpty() && isHTMLImageElement(*elements.first());
+    if (onlyMatchImg)

[sof, 2015/11/13 08:21:48]

Hmm, what if the <img> element doesn't appear first and/or there are multiple
with that id/name?

[tkent, 2015/11/13 08:28:25]

I'd like to count only cases where this function returns an IMG element or
RadioNodeList with IMG elements. The current code is enough because
RadioNodeList with onlyMatchImg=false won't include IMG elements.

[sof, 2015/11/13 08:33:10]

Yes, this looks correct & precise as-is -- step 2 from
https://html.spec.whatwg.org/multipage/forms.html#dom-form-nameditem will only
return IMGs and never a list with IMGs mixed in. lgtm.

+        UseCounter::count(document(), UseCounter::FormNameAccessForImageElement);
     if (elements.size() == 1) {
         returnValue.setElement(elements.at(0));
         return;
     }
 
-    bool onlyMatchImg = !elements.isEmpty() && isHTMLImageElement(*elements.first());
     returnValue.setRadioNodeList(radioNodeList(name, onlyMatchImg));
 }
 
 void HTMLFormElement::setDemoted(bool demoted)
 {
     if (demoted)
         UseCounter::count(document(), UseCounter::DemotedFormElement);
     m_wasDemoted = demoted;
 }
 
 } // namespace