Add two UseCounters for form.imageName and form.elements.imageName.

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 794 matching lines @@
             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)
+    if (onlyMatchImg) {
         UseCounter::count(document(), UseCounter::FormNameAccessForImageElement);
+        // The following code has performance impact, but it should be small
+        // because <img> access via <form> name getter is rarely used.
+        for (auto& element : elements) {
+            if (isHTMLImageElement(*element) && !element->isDescendantOf(this)) {
+                UseCounter::count(document(), UseCounter::FormNameAccessForNonDescendantImageElement);
+                break;
+            }
+        }
+    }
     if (elements.size() == 1) {
         returnValue.setElement(elements.at(0));
         return;
     }
 
     returnValue.setRadioNodeList(radioNodeList(name, onlyMatchImg));
 }
 
 void HTMLFormElement::setDemoted(bool demoted)
 {
     if (demoted)
         UseCounter::count(document(), UseCounter::DemotedFormElement);
     m_wasDemoted = demoted;
 }
 
 } // namespace