REGRESSION: SVG <a> elmenet ignores tabsToLinks setting

The regression caused by Blink r155290, which removed an argumetn of
isKeyboardFocusable. We forgot to remove the argument for
SVGAElement::isKeyboardFocusable.

BUG=276105
TEST=automated

Review URL: https://chromiumcodereview.appspot.com/22865021

git-svn-id: svn://svn.chromium.org/blink/trunk@156373 bbb929c8-8fbe-4397-9dbb-9b2b20218538