[MDBViz] Switch from a QListView to a QTreeView for the ops

This lets us open & close groups and automates the hierarchy.

Change-Id: Ib6f0850a49b793d824fc25aa16be78e6a1a93d9e
Reviewed-on: https://skia-review.googlesource.com/43280
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
5 files changed