Add specialized impl of Wang's formula for cubic rationals
Add specialized impl of Wang's formula for cubic rationals

Initial data suggests that the non-rational Wang's formula does not
form an upper bound for the rational case, so additional work is needed
to handle them. Note this new formula is not actually due to Wang,
but is an analogue.

The version added in this CL is for cubic rationals because the current
tessellation code promotes all curve segments to cubic rationals for
ease. If we end up using this approach, it would be likely simpler and
faster to implement the degree-2 version and handle conics separately
during tessellation.

From:
J. Zheng, T. Sederberg. "Estimating Tessellation Parameter Intervals for
Rational Curves and Surfaces." ACM Transactions on Graphics 19(1). 2000.

Bug: skia:10419
Change-Id: Ie02e229c089541ece05c7502217b1ef5d4799b52
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/337720
Commit-Queue: Tyler Denniston <293ae2d31b7e9da32c4fb58bdaaed1f4bef4c6e7@google.com>
Reviewed-by: Chris Dalton <ef7fc3a08ada7d31f16e9a18b5f3c728256e041e@google.com>

aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia