Fix fuzzer assert in GradientShaderBase4fContext::TSampler
Fix fuzzer assert in GradientShaderBase4fContext::TSampler

The arithmetic in tileProc<kMirror> may cause the result to snap to the
open interval value - which violates invariants down the line.

We need to clamp the result to nextafterf(2, 0) to ensure it stays less
than two.

BUG=skia:5913
R=reed@google.com,herb@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2472763002

Review-Url: https://codereview.chromium.org/2472763002

HalCanary/skia-hc,HalCanary/skia-hc,google/skia,rubenvb/skia,google/skia,HalCanary/skia-hc,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,aosp-mirror/platform_external_skia,Hikari-no-Tenshi/android_external_skia,google/skia,HalCanary/skia-hc,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,aosp-mirror/platform_external_skia,google/skia,rubenvb/skia,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,rubenvb/skia,aosp-mirror/platform_external_skia,rubenvb/skia,HalCanary/skia-hc,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,rubenvb/skia,aosp-mirror/platform_external_skia,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,HalCanary/skia-hc,aosp-mirror/platform_external_skia,google/skia,google/skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,google/skia,HalCanary/skia-hc,aosp-mirror/platform_external_skia,google/skia,google/skia,Hikari-no-Tenshi/android_external_skia,rubenvb/skia