Require Sk4f::toBytes() clamps

src/opts/SkNx_sse.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkNx_sse_DEFINED
 #define SkNx_sse_DEFINED
 
@@ skipping 159 matching lines @@
     }
 
     SkNf(float a, float b, float c, float d) : fVec(_mm_setr_ps(a,b,c,d)) {}
 
     void store(float vals[4]) const { _mm_storeu_ps(vals, fVec); }
     void toBytes(uint8_t bytes[4]) const {
         __m128i fix8_32 = _mm_cvttps_epi32(fVec),
                 fix8_16 = _mm_packus_epi16(fix8_32, fix8_32),
                 fix8    = _mm_packus_epi16(fix8_16, fix8_16);
         *(int*)bytes = _mm_cvtsi128_si32(fix8);
-        // TODO: use _mm_shuffle_epi8 w/SSSE3?
     }
 
     SkNi<4, int> castTrunc() const { return _mm_cvttps_epi32(fVec); }
 
     SkNf operator + (const SkNf& o) const { return _mm_add_ps(fVec, o.fVec); }
     SkNf operator - (const SkNf& o) const { return _mm_sub_ps(fVec, o.fVec); }
     SkNf operator * (const SkNf& o) const { return _mm_mul_ps(fVec, o.fVec); }
     SkNf operator / (const SkNf& o) const { return _mm_div_ps(fVec, o.fVec); }
 
     SkNf operator == (const SkNf& o) const { return _mm_cmpeq_ps (fVec, o.fVec); }
@@ skipping 139 matching lines @@
         return _mm_or_si128(_mm_and_si128   (fVec, t.fVec),
                             _mm_andnot_si128(fVec, e.fVec));
     }
 
     __m128i fVec;
 };
 
 }  // namespace
 
 #endif//SkNx_sse_DEFINED