At the moment it uses custom call to ScriptExecutionContext::reportException while the exceptions should be reported in a regular way using V8 message listener set in V8DOMWindowShell::initContextIfNeeded.
Created attachment 69185 [details] Patch
Comment on attachment 69185 [details] Patch LGTM, much nicer
Comment on attachment 69185 [details] Patch Clearing flags on attachment: 69185 Committed r68641: <http://trac.webkit.org/changeset/68641>
All reviewed patches have been landed. Closing bug.