- Turbolizer highlights input and output nodes on hover.
- The three panes support resizing now (snap to side still works).

Bug: 
Change-Id: Ida1513fd714a02ab772885ea1fdf6d9da8d540f6
Reviewed-on: https://chromium-review.googlesource.com/837068
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Daniel Clifford <danno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50523}