Update SkPMFloat API a bit.

src/opts/SkPMFloat_SSSE3.h

 #include "SkColorPriv.h"
 #include <tmmintrin.h>
 
-// For set(), we widen our 8 bit components (fix8) to 8-bit components in 32 bits (fix8_32),
-// then convert those to floats.
+// For SkPMFloat(SkPMColor), we widen our 8 bit components (fix8) to 8-bit components in 32 bits
+// (fix8_32), then convert those to floats.
 
 // get() does the opposite, working from floats to 8-bit-in-32-bits, then back to packed 8 bit.
 
 // clamped() is the same as _SSE2: floats to 8-in-32, to 8-in-16, to packed 8 bit, with
 // _mm_packus_epi16() both clamping and narrowing.
 
-inline void SkPMFloat::set(SkPMColor c) {
+inline SkPMFloat::SkPMFloat(SkPMColor c) {
     SkPMColorAssert(c);
     const int _ = 255;  // _ means to zero that byte.
     __m128i fix8    = _mm_set_epi32(0,0,0,c),
             fix8_32 = _mm_shuffle_epi8(fix8, _mm_set_epi8(_,_,_,3, _,_,_,2, _,_,_,1, _,_,_,0));
     _mm_store_ps(fColor, _mm_cvtepi32_ps(fix8_32));
     SkASSERT(this->isValid());
 }
 
 inline SkPMColor SkPMFloat::get() const {
     SkASSERT(this->isValid());
     const int _ = 255;  // _ means to zero that byte.
     __m128i fix8_32 = _mm_cvtps_epi32(_mm_load_ps(fColor)),  // _mm_cvtps_epi32 rounds for us!
             fix8    = _mm_shuffle_epi8(fix8_32, _mm_set_epi8(_,_,_,_, _,_,_,_, _,_,_,_, 12,8,4,0));
     SkPMColor c = _mm_cvtsi128_si32(fix8);
     SkPMColorAssert(c);
     return c;
 }
 
 inline SkPMColor SkPMFloat::clamped() const {
     __m128i fix8_32 = _mm_cvtps_epi32(_mm_load_ps(fColor)),  // _mm_cvtps_epi32 rounds for us!
             fix8_16 = _mm_packus_epi16(fix8_32, fix8_32),
             fix8    = _mm_packus_epi16(fix8_16, fix8_16);
     SkPMColor c = _mm_cvtsi128_si32(fix8);
     SkPMColorAssert(c);
     return c;
 }