AudioPlayer: Update volume controls.
This CL includes:
- Custom volume slider is replaced with paper-slider, which is dynamically shown on the top of control panel when volume button is activated.
BUG=
488229
Committed:
https://crrev.com/8847bc03c848c4f5dab165b9cb796a79ec69ef72
Cr-Commit-Position: refs/heads/master@{#357069}