Weight the D point heavily during nonlinear regression

This helps enforce that the linear and non-linear portions line up.
Include the gap at 'D' in the profile output for approximated curves.

Change-Id: Ie79aa79e35dbf962b44d822a5f1cfe963e546d03
Reviewed-on: https://skia-review.googlesource.com/118620
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
19 files changed