Change in focus with movement of Arrow keys for RTL radio buttons.

Updated the function findNextFocusableRadioButtonInGroup to
take into consideration the computedTextDirection for
deciding which radio button to move the focus on.

BUG=556677

Review URL: https://codereview.chromium.org/1633553002

Cr-Commit-Position: refs/heads/master@{#374652}
3 files changed