Clean up code for custom slide GUIs

Bailing out early caused controls to flicker on/off if one was being
interacted with. No need to rebuild the window (paramsChanged), the GUI
is up, so we're already repainting.

Change-Id: I0751271962075dff22b19f60f4d1dc81c9232f58
Reviewed-on: https://skia-review.googlesource.com/145335
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed