Minor shadow fixes.

Fix inset value for analytic shadows to get full inset (and hence
proper falloff).
Fix compute_radial_values in tessellator to return only positive values
and produce cleaner arcs.
Adjust shadow params in Android sample to match Android.
Fix corner calculation for analytic shadow.

Bug: skia:7486
Change-Id: Ib393b5d577f5a5eb89d3388aa4726ea4dae37055
Reviewed-on: https://skia-review.googlesource.com/123220
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
4 files changed