add 'R' to toggle rasterpipeline in sampleapp

Bug: skia:
Change-Id: I5b198c883140a281d9304fe3c44978cd8fcabce9
Reviewed-on: https://skia-review.googlesource.com/31461
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
1 file changed