Change PRESUBMIT.py to use [Get|Update]DescriptionLines

This should fix the "git cl upload" failures on the recipe roller.

Change-Id: I1c433a5a6dc7f52034bef8b2178b3041b8f4661e
Reviewed-on: https://skia-review.googlesource.com/11020
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Eric Boren <borenet@google.com>
1 file changed