Add special case circle blur for Ganesh

src/core/SkColor.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkColor.h"
 #include "SkColorPriv.h"
 #include "SkFixed.h"
@@ skipping 52 matching lines @@
     if (h < 0) {
         h += SkIntToScalar(360);
     }
     SkASSERT(h >= 0 && h < SkIntToScalar(360));
 
     hsv[0] = h;
     hsv[1] = s;
     hsv[2] = v;
 }
 
-static inline U8CPU UnitScalarToByte(SkScalar x) {
-    if (x < 0) {
-        return 0;
-    }
-    if (x >= SK_Scalar1) {
-        return 255;
-    }
-    return SkScalarToFixed(x) >> 8;
-}
-
 SkColor SkHSVToColor(U8CPU a, const SkScalar hsv[3]) {
     SkASSERT(hsv);
 
-    U8CPU s = UnitScalarToByte(hsv[1]);
-    U8CPU v = UnitScalarToByte(hsv[2]);
+    U8CPU s = SkUnitScalarClampToByte(hsv[1]);
+    U8CPU v = SkUnitScalarClampToByte(hsv[2]);
 
     if (0 == s) { // shade of gray
         return SkColorSetARGB(a, v, v, v);
     }
     SkFixed hx = (hsv[0] < 0 || hsv[0] >= SkIntToScalar(360)) ? 0 : SkScalarToFixed(hsv[0]/60);
     SkFixed f = hx & 0xFFFF;
 
     unsigned v_scale = SkAlpha255To256(v);
     unsigned p = SkAlphaMul(255 - s, v_scale);
     unsigned q = SkAlphaMul(255 - (s * f >> 16), v_scale);
     unsigned t = SkAlphaMul(255 - (s * (SK_Fixed1 - f) >> 16), v_scale);
 
     unsigned r, g, b;
 
     SkASSERT((unsigned)(hx >> 16) < 6);
     switch (hx >> 16) {
         case 0: r = v; g = t; b = p; break;
         case 1: r = q; g = v; b = p; break;
         case 2: r = p; g = v; b = t; break;
         case 3: r = p; g = q; b = v; break;
         case 4: r = t;  g = p; b = v; break;
         default: r = v; g = p; b = q; break;
     }
     return SkColorSetARGB(a, r, g, b);
 }