Set analytic AA as default.

src/core/SkScan_AAAPath.cpp

 /*
  * Copyright 2016 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 "SkAntiRun.h"
 #include "SkBlitter.h"
 #include "SkEdge.h"
@@ skipping 463 matching lines @@
     // return ((((a >> 8) * (a >> 8)) >> 8) * (b >> 8)) >> 1;
     return (a >> 11) * (a >> 11) * (b >> 11);
 }
 
 // The alpha of right-triangle (a, a*b)
 static inline SkAlpha partialTriangleToAlpha(SkFixed a, SkFixed b) {
     return partialTriangleToAlpha16(a, b) >> 8;
 }
 
 static inline SkAlpha getPartialAlpha(SkAlpha alpha, SkFixed partialHeight) {
-    return (alpha * partialHeight + SK_FixedHalf) >> 16;
+    return SkToU8(SkFixedRoundToInt(alpha * partialHeight));
 }
 
 static inline SkAlpha getPartialAlpha(SkAlpha alpha, SkAlpha fullAlpha) {
     return ((uint16_t)alpha * fullAlpha) >> 8;
 }
 
 // For SkFixed that's close to SK_Fixed1, we can't convert it to alpha by just shifting right.
 // For example, when f = SK_Fixed1, right shifting 8 will get 256, but we need 255.
 // This is rarely the problem so we'll only use this for blitting rectangles.
 static inline SkAlpha f2a(SkFixed f) {
@@ skipping 849 matching lines @@
         AAAFillPath(path, clip.bwRgn(), blitter);
     } else {
         SkRegion        tmp;
         SkAAClipBlitter aaBlitter;
 
         tmp.setRect(clip.getBounds());
         aaBlitter.init(blitter, &clip.aaRgn());
         AAAFillPath(path, tmp, &aaBlitter, true);
     }
 }