Set analytic AA as default.

src/core/SkAntiRun.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 SkAntiRun_DEFINED
 #define SkAntiRun_DEFINED
 
 #include "SkBlitter.h"
 
 /** Sparse array of run-length-encoded alpha (supersampling coverage) values.
     Sparseness allows us to independently compose several paths into the
     same SkAlphaRuns buffer.
 */
 
 class SkAlphaRuns {
 public:
     int16_t*    fRuns;
     uint8_t*     fAlpha;
 
     // Return 0-255 given 0-256
     static inline SkAlpha CatchOverflow(int alpha) {
+        SkASSERT(alpha >= 0 && alpha <= 256);
         return alpha - (alpha >> 8);
     }
 
     /// Returns true if the scanline contains only a single run,
     /// of alpha value 0.
     bool empty() const {
         SkASSERT(fRuns[0] > 0);
         return fAlpha[0] == 0 && fRuns[fRuns[0]] == 0;
     }
 
@@ skipping 150 matching lines @@
             x -= n;
         }
     }
 
 private:
     SkDEBUGCODE(int fWidth;)
     SkDEBUGCODE(void validate() const;)
 };
 
 #endif