What did we learn today?  255 != 256
What did we learn today?  255 != 256

vcvt_n_f32_u32 and _u32_f32 work in power-of-2 fixed point, so (...,8)
meant 'please multiply or divide by 256'.  We need to use 255.  :(

BUG=skia:

Review URL: https://codereview.chromium.org/1204363002

google/skia,ominux/skia,shahrzadmn/skia,Jichao/skia,google/skia,ominux/skia,vanish87/skia,todotodoo/skia,pcwalton/skia,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,nvoron23/skia,aosp-mirror/platform_external_skia,Hikari-no-Tenshi/android_external_skia,google/skia,aosp-mirror/platform_external_skia,nvoron23/skia,todotodoo/skia,noselhq/skia,qrealka/skia-hc,Hikari-no-Tenshi/android_external_skia,shahrzadmn/skia,google/skia,google/skia,qrealka/skia-hc,vanish87/skia,pcwalton/skia,rubenvb/skia,HalCanary/skia-hc,rubenvb/skia,todotodoo/skia,nvoron23/skia,ominux/skia,qrealka/skia-hc,rubenvb/skia,ominux/skia,noselhq/skia,pcwalton/skia,todotodoo/skia,aosp-mirror/platform_external_skia,ominux/skia,pcwalton/skia,qrealka/skia-hc,noselhq/skia,rubenvb/skia,noselhq/skia,ominux/skia,aosp-mirror/platform_external_skia,Hikari-no-Tenshi/android_external_skia,nvoron23/skia,google/skia,shahrzadmn/skia,Jichao/skia,HalCanary/skia-hc,shahrzadmn/skia,google/skia,tmpvar/skia.cc,Jichao/skia,noselhq/skia,vanish87/skia,pcwalton/skia,nvoron23/skia,shahrzadmn/skia,Hikari-no-Tenshi/android_external_skia,tmpvar/skia.cc,aosp-mirror/platform_external_skia,shahrzadmn/skia,todotodoo/skia,pcwalton/skia,noselhq/skia,Hikari-no-Tenshi/android_external_skia,aosp-mirror/platform_external_skia,Jichao/skia,tmpvar/skia.cc,nvoron23/skia,noselhq/skia,tmpvar/skia.cc,aosp-mirror/platform_external_skia,ominux/skia,HalCanary/skia-hc,HalCanary/skia-hc,pcwalton/skia,aosp-mirror/platform_external_skia,google/skia,qrealka/skia-hc,tmpvar/skia.cc,qrealka/skia-hc,tmpvar/skia.cc,vanish87/skia,HalCanary/skia-hc,pcwalton/skia,shahrzadmn/skia,ominux/skia,nvoron23/skia,nvoron23/skia,shahrzadmn/skia,Jichao/skia,rubenvb/skia,Jichao/skia,vanish87/skia,Jichao/skia,HalCanary/skia-hc,aosp-mirror/platform_external_skia,vanish87/skia,Hikari-no-Tenshi/android_external_skia,vanish87/skia,qrealka/skia-hc,google/skia,tmpvar/skia.cc,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,qrealka/skia-hc,HalCanary/skia-hc,todotodoo/skia,noselhq/skia,vanish87/skia,tmpvar/skia.cc,HalCanary/skia-hc,vanish87/skia,tmpvar/skia.cc,pcwalton/skia,rubenvb/skia,rubenvb/skia,rubenvb/skia,nvoron23/skia,ominux/skia,Jichao/skia,rubenvb/skia,todotodoo/skia,shahrzadmn/skia,todotodoo/skia,noselhq/skia,Jichao/skia,todotodoo/skia,aosp-mirror/platform_external_skia,google/skia