Fix for ::selection pseudo element to work on input elements

When text is selected inside input element, it should change the
color and background color according to the ::selection pseudo
element.

BUG=167676

Review URL: https://codereview.chromium.org/220343006

git-svn-id: svn://svn.chromium.org/blink/trunk@171467 bbb929c8-8fbe-4397-9dbb-9b2b20218538