Use SkMScalar as float by default to match Chromium.

include/core/SkPostConfig.h

Index: include/core/SkPostConfig.h
diff --git a/include/core/SkPostConfig.h b/include/core/SkPostConfig.h
index 37e6c591d980bde0b1b670121ad175a203f927dd..1508b1a2ff07b3e9c463dbe2c0fb838d020c16b7 100644
--- a/include/core/SkPostConfig.h
+++ b/include/core/SkPostConfig.h
@@ -24,13 +24,12 @@
 
 /**
  * Matrix calculations may be float or double.
- * The default is double, as that is faster given our impl uses doubles
- * for intermediate calculations.
+ * The default is float, as that's what Chromium's using.
  */
 #if defined(SK_MSCALAR_IS_DOUBLE) && defined(SK_MSCALAR_IS_FLOAT)
 #  error "cannot define both SK_MSCALAR_IS_DOUBLE and SK_MSCALAR_IS_FLOAT"
 #elif !defined(SK_MSCALAR_IS_DOUBLE) && !defined(SK_MSCALAR_IS_FLOAT)
-#  define SK_MSCALAR_IS_DOUBLE
+#  define SK_MSCALAR_IS_FLOAT
 #endif
 
 #if defined(SK_CPU_LENDIAN) && defined(SK_CPU_BENDIAN)