Revert of Support Float32 output from SkColorSpaceXform

src/core/SkPM4fPriv.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPM4fPriv_DEFINED
 #define SkPM4fPriv_DEFINED
 
@@ skipping 37 matching lines @@
 }
 
 
 // SkColor handling:
 //   SkColor has an ordering of (b, g, r, a) if cast to an Sk4f, so the code swizzles r and b to
 // produce the needed (r, g, b, a) ordering.
 static inline Sk4f Sk4f_from_SkColor(SkColor color) {
     return swizzle_rb(Sk4f_fromS32(color));
 }
 
+static inline void assert_unit(float x) {
+    SkASSERT(0 <= x && x <= 1);
+}
+
+static inline float exact_srgb_to_linear(float srgb) {
+    assert_unit(srgb);
+    float linear;
+    if (srgb <= 0.04045) {
+        linear = srgb / 12.92f;
+    } else {
+        linear = powf((srgb + 0.055f) / 1.055f, 2.4f);
+    }
+    assert_unit(linear);
+    return linear;
+}
+
 #endif