Match html5 unquoted attribute parsing
* Brings us closer to the html5 attribute parsing algorithm described
in http://www.w3.org/TR/html5/syntax.html#before-attribute-value-state
* There's a similar patch for the Parsoid in,
I2160a23b2a3c914eb369347bbf5d58328440041d
* The spec says <div class= style="123">hi</div> should parse as
<div class="style=\"123\"">hi</div>, which it now does, whereas it
used to yield <div class="" style="123">hi</div>.
* Merge with caution. This is going to break pages like,
frwikisource/La_Mirlitantouille_(Lenotre)?oldid=
4669681
Bug: T108134
Change-Id: Ic2fc1b573a55a847e6c05707678b58c1189ecc52