Use first/second instead of min/max in 2pt conical gradient

Here's the tiny performance gain:

$python tools/calmbench/calmbench.py firstsecond --extraarg "-m conic"

firstsecond (compared to master) is likely
    4.23% faster in gradient_conicalOut_clamp_3color
    4.23% faster in gradient_conicalOutZero_clamp_3color
    4.79% faster in gradient_conical_clamp_shallow_dither
    6.04% faster in gradient_conical_clamp_3color
    6.04% faster in gradient_conicalZero_clamp_3color
    6.42% faster in gradient_conicalOut_clamp
    6.43% faster in gradient_conicalOutZero_clamp
    6.74% faster in gradient_conical_clamp
    6.98% faster in gradient_conical_clamp_shallow
    6.98% faster in gradient_conicalZero_clamp

Bug: skia:
Change-Id: Id74866908b99753ed8b16a657d3f67c9255d0043
Reviewed-on: https://skia-review.googlesource.com/76561
Commit-Queue: Yuqian Li <liyuqian@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
Reviewed-by: Florin Malita <fmalita@chromium.org>
6 files changed