check for 0x8000 before calling abs
check for 0x8000 before calling abs

Bug: oss-fuzz:6124
Change-Id: I1897a4ce8f6e60bf93b9e6579725443763e8d287
Reviewed-on: https://skia-review.googlesource.com/125342
Reviewed-by: Florin Malita <a8262bf13ea8c26821e91ea9bca6740a77c96dcd@chromium.org>
Commit-Queue: Mike Reed <f5cabf8735907151a446812c9875d6c0c712d847@google.com>

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