Fix transparent ambient for perspective shadows

When splitting the long edges for the ambient code, I wasn't adding
the corresponding triangle for the new point into the center region
for transparent occluders.

Change-Id: Ie2d1dcffbd701c0750d5da95e9d673b700a0e85a
Reviewed-on: https://skia-review.googlesource.com/16492
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
1 file changed