Move float<->byte conversions into Sk4f.

src/opts/SkPMFloat_none.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.
- */
-
-namespace {  // See SkPMFloat.h
-
-inline SkPMFloat::SkPMFloat(SkPMColor c) {
-    float inv255 = 1.0f/255;
-    *this = SkPMFloat::FromARGB(SkGetPackedA32(c) * inv255,
-                                SkGetPackedR32(c) * inv255,
-                                SkGetPackedG32(c) * inv255,
-                                SkGetPackedB32(c) * inv255);
-    SkASSERT(this->isValid());
-}
-
-inline SkPMColor SkPMFloat::round() const {
-    float a = this->a(),
-          r = this->r(),
-          g = this->g(),
-          b = this->b();
-    a = a < 0 ? 0 : (a > 1 ? 1 : a);
-    r = r < 0 ? 0 : (r > 1 ? 1 : r);
-    g = g < 0 ? 0 : (g > 1 ? 1 : g);
-    b = b < 0 ? 0 : (b > 1 ? 1 : b);
-    SkPMColor c = SkPackARGB32(255*a+0.5f, 255*r+0.5f, 255*g+0.5f, 255*b+0.5f);
-    SkPMColorAssert(c);
-    return c;
-}
-
-inline Sk4f SkPMFloat::alphas() const {
-    return Sk4f(this->a());
-}
-
-inline SkPMFloat SkPMFloat::FromOpaqueColor(SkColor c) {
-  SkASSERT(SkColorGetA(c) == 0xFF);
-  float inv255 = 1.0f / 255;
-  SkPMFloat pmf = SkPMFloat::FromARGB(1.0f,
-                                      SkColorGetR(c) * inv255,
-                                      SkColorGetG(c) * inv255,
-                                      SkColorGetB(c) * inv255);
-  SkASSERT(pmf.isValid());
-  return pmf;
-}
-
-}  // namespace