Video Tutorials : Using RadioButtonWithDescription

This CL changes the radio button in language picker from using a linear
layout to use RadioButtonWithDescription. Also disable the watch button
initially when no radio button is checked.

Bug: 1117182
Change-Id: I836947d6484c57760c6e6fd9b0d2450d8ce8d6eb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2492906


Reviewed-by: Xing Liu <xingliu@chromium.org>
Commit-Queue: Shakti Sahu <shaktisahu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#820062}