Add special case circle blur for Ganesh

include/core/SkColorPriv.h

 /*
  * 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.
  */
 
 #ifndef SkColorPriv_DEFINED
 #define SkColorPriv_DEFINED
 
@@ skipping 200 matching lines @@
 static inline int SkAlphaBlend255(S16CPU src, S16CPU dst, U8CPU alpha) {
     SkASSERT((int16_t)src == src);
     SkASSERT((int16_t)dst == dst);
     SkASSERT((uint8_t)alpha == alpha);
 
     int prod = (src - dst) * alpha + 128;
     prod = (prod + (prod >> 8)) >> 8;
     return dst + prod;
 }
 
+static inline U8CPU SkUnitScalarClampToByte(SkScalar x) {
+    if (x < 0) {
+        return 0;
+    }
+    if (x >= SK_Scalar1) {
+        return 255;
+    }
+    return SkScalarToFixed(x) >> 8;
+}
+
 #define SK_R16_BITS     5
 #define SK_G16_BITS     6
 #define SK_B16_BITS     5
 
 #define SK_R16_SHIFT    (SK_B16_BITS + SK_G16_BITS)
 #define SK_G16_SHIFT    (SK_B16_BITS)
 #define SK_B16_SHIFT    0
 
 #define SK_R16_MASK     ((1 << SK_R16_BITS) - 1)
 #define SK_G16_MASK     ((1 << SK_G16_BITS) - 1)
@@ skipping 812 matching lines @@
     int srcG = SkColorGetG(src);
     int srcB = SkColorGetB(src);
 
     for (int i = 0; i < width; i++) {
         dst[i] = SkBlendLCD16Opaque(srcR, srcG, srcB, dst[i], mask[i],
                                     opaqueDst);
     }
 }
 
 #endif