use linear segment instead of recalculating it

Change-Id: I55f8e5d23f7f77681f45cfe2255ef8dda416497f
Reviewed-on: https://skia-review.googlesource.com/123583
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Mike Klein <mtklein@chromium.org>
6 files changed