Crash in blink::getTypeExtension

third_party/WebKit/Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
@@ skipping 671 matching lines @@
     UseCounter::count(document,
                       UseCounter::DocumentCreateElement2ndArgStringHandling);
     return stringOrOptions.getAsString();
   }
 
   if (stringOrOptions.isDictionary()) {
     Dictionary dict = stringOrOptions.getAsDictionary();
     ElementCreationOptions impl;
     V8ElementCreationOptions::toImpl(dict.isolate(), dict.v8Value(), impl,
                                      exceptionState);
+    if (exceptionState.hadException())
+      return emptyString();
+
     if (impl.hasIs())
       return impl.is();
 
-    return toCoreString(dict.v8Value()->ToString());
+    // Do not handle stringification, but count it as a string handling

[dominicc (has gone to gerrit), 2017/01/19 05:34:46]

This changes behavior because we won't toString the argument now. I would not
use count this path with this counter, because this path is already changed. If
you want to count it at all, I would add a second counter.

[Anton Obzhirov, 2017/01/19 16:45:44]

I think no need to count this case it should be very rare.

+    UseCounter::count(document,
+                      UseCounter::DocumentCreateElement2ndArgStringHandling);
   }
 
   return emptyString();
 }
 
 // https://dom.spec.whatwg.org/#dom-document-createelement
 Element* Document::createElement(const AtomicString& localName,
                                  const StringOrDictionary& stringOrOptions,
                                  ExceptionState& exceptionState) {
   // 1. If localName does not match Name production, throw InvalidCharacterError
@@ skipping 5882 matching lines @@
 }
 
 void showLiveDocumentInstances() {
   WeakDocumentSet& set = liveDocumentSet();
   fprintf(stderr, "There are %u documents currently alive:\n", set.size());
   for (Document* document : set)
     fprintf(stderr, "- Document %p URL: %s\n", document,
             document->url().getString().utf8().data());
 }
 #endif