GitLab

- Removes media-router-sink custom element.
- Removes media-router-sink-picker custom element.
- Replaces media-router-sink with paper-item (material).
- Replaces media-router-sink-picker with core-menu.
- Removes sink type icons.

Review URL: https://codereview.chromium.org/1133853003

Cr-Commit-Position: refs/heads/master@{#329312}