Include line numbers in Viewer's shader error windows

Change-Id: I83bea6e9c94431afba858b0e7b60456e8f9a2176
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/260356
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
4 files changed