Make StyleSheetList.item() index argument mandatory

Make StyleSheetList.item() index argument mandatory to match the specification:
http://www.w3.org/TR/2000/CR-DOM-Level-2-20000510/stylesheets.html#StyleSheets-StyleSheetList

This behavior is consistent with Firefox 23. The argument is however optional
in IE10, which is uncommon for an indexed getter.

BUG=

Review URL: https://chromiumcodereview.appspot.com/23629011

git-svn-id: svn://svn.chromium.org/blink/trunk@157054 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make index argument to HTMLOptionsCollection.remove() mandatory

Make index argument to HTMLOptionsCollection.remove() mandatory as per the
specification:
http://www.whatwg.org/specs/web-apps/current-work/multipage/common-dom-interfaces.html#htmloptionscollection-0

This behavior is consistent with Firefox 23 and IE10. It is confusing what
is expected to happen when no argument is given.

BUG=

Review URL: https://chromiumcodereview.appspot.com/23602016

git-svn-id: svn://svn.chromium.org/blink/trunk@157055 bbb929c8-8fbe-4397-9dbb-9b2b20218538