Use renderStyle() instead of renderer()->style() in TextControlInnerElement::customStyleForRenderer().

BUG=none

Review URL: https://chromiumcodereview.appspot.com/23137007

git-svn-id: svn://svn.chromium.org/blink/trunk@156370 bbb929c8-8fbe-4397-9dbb-9b2b20218538