SkColorCubeFilter: require alpha == 0xFF.

src/opts/SkPMFloat_neon.h

Index: src/opts/SkPMFloat_neon.h
diff --git a/src/opts/SkPMFloat_neon.h b/src/opts/SkPMFloat_neon.h
index ecb151f1fdb70dad1b18190281150ba29c4549d4..4e099f91ecce2593719c211a32bf408bcac2bf1b 100644
--- a/src/opts/SkPMFloat_neon.h
+++ b/src/opts/SkPMFloat_neon.h
@@ -33,14 +33,14 @@ inline Sk4f SkPMFloat::alphas() const {
     return vdupq_lane_f32(vget_high_f32(fVec), 1);  // Duplicate high lane of high half i.e. lane 3.
 }
 
-inline SkPMFloat SkPMFloat::FromBGRx(SkColor c) {
+inline SkPMFloat SkPMFloat::FromOpaqueColor(SkColor c) {
+    SkASSERT(SkColorGetA(c) == 0xFF);
     uint8x8_t fix8 = (uint8x8_t)vdup_n_u32(c);
 #if defined(SK_PMCOLOR_IS_RGBA)
     fix8 = vtbl1_u8(fix8, vcreate_u8(0x0300010203000102ULL));  // 03 00 01 02, 2x, i.e. swap R&B.
 #endif
     uint16x8_t fix8_16 = vmovl_u8(fix8);
     uint32x4_t fix8_32 = vmovl_u16(vget_low_u16(fix8_16));
-    fix8_32 = vsetq_lane_u32(0xFF, fix8_32, 3);  // Force alpha to 1.
 
     SkPMFloat pmf = Sk4f(vmulq_f32(vcvtq_f32_u32(fix8_32), vdupq_n_f32(1.0f/255)));
     SkASSERT(pmf.isValid());