Add wireframe mode to Viewer.

Change-Id: I0ff11088465a4702acf9841a791d76f286ddbaf1
Reviewed-on: https://skia-review.googlesource.com/15147
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
17 files changed