HTMLTableRowElement.insertCell()'s argument default value should be -1

HTMLTableRowElement.insertCell()'s argument default value should be -1, not
0, as per the specification:
http://www.whatwg.org/specs/web-apps/current-work/multipage/tabular-data.html#the-tr-element

The new behavior matches the one of Firefox 29 and IE11.

R=arv@chromium.org, eseidel@chromium.org
BUG=369803
TEST=fast/dom/HTMLTableRowElement/insertCell-default-argument.html

Review URL: https://codereview.chromium.org/263323004

git-svn-id: svn://svn.chromium.org/blink/trunk@173422 bbb929c8-8fbe-4397-9dbb-9b2b20218538