Don't create GrAtlasTextBlobs for zero glyph count text draws.

Bug: chromium:749472

Change-Id: I709889dd6bb06032e30cbf820ca67e7534cfac58
Reviewed-on: https://skia-review.googlesource.com/28540
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
1 file changed