use floor for mip-level choice

src/core/SkMipMap.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkMipMap.h"
 #include "SkBitmap.h"
 #include "SkColorPriv.h"
@@ skipping 316 matching lines @@
 
     if (scale >= SK_Scalar1 || scale <= 0 || !SkScalarIsFinite(scale)) {
         return false;
     }
 
     SkScalar L = -SkScalarLog2(scale);
     if (!SkScalarIsFinite(L)) {
         return false;
     }
     SkASSERT(L >= 0);
+#ifdef SK_SUPPORT_LEGACY_ROUND_MIPMAP_LEVEL_CHOICE
     int level = SkScalarRoundToInt(L);
-//    SkDebugf("mipmap scale=%g L=%g level=%d\n", scale, L, level);
+#else
+//    int rndLevel = SkScalarRoundToInt(L);
+    int level = SkScalarFloorToInt(L);
+#endif
+//    SkDebugf("mipmap scale=%g L=%g level=%d rndLevel=%d\n", scale, L, level, rndLevel);
 
     SkASSERT(level >= 0);
     if (level <= 0) {
         return false;
     }
 
     if (level > fCount) {
         level = fCount;
     }
     if (levelPtr) {
         *levelPtr = fLevels[level - 1];
     }
     return true;
 }