Use SkMScalar as float by default to match Chromium.

include/core/SkPostConfig.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 SkPostConfig_DEFINED
 #define SkPostConfig_DEFINED
 
 #if defined(SK_BUILD_FOR_WIN32) || defined(SK_BUILD_FOR_WINCE)
 #  define SK_BUILD_FOR_WIN
 #endif
 
 #if defined(SK_DEBUG) && defined(SK_RELEASE)
 #  error "cannot define both SK_DEBUG and SK_RELEASE"
 #elif !defined(SK_DEBUG) && !defined(SK_RELEASE)
 #  error "must define either SK_DEBUG or SK_RELEASE"
 #endif
 
 #if defined(SK_SUPPORT_UNITTEST) && !defined(SK_DEBUG)
 #  error "can't have unittests without debug"
 #endif
 
 /**
  * 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)
 #  error "cannot define both SK_CPU_LENDIAN and SK_CPU_BENDIAN"
 #elif !defined(SK_CPU_LENDIAN) && !defined(SK_CPU_BENDIAN)
 #  error "must define either SK_CPU_LENDIAN or SK_CPU_BENDIAN"
 #endif
 
 /**
  * Ensure the port has defined all of SK_X32_SHIFT, or none of them.
@@ skipping 327 matching lines @@
 #  define SK_GAMMA_EXPONENT (2.2f)
 #endif
 
 //////////////////////////////////////////////////////////////////////
 
 #ifndef GR_TEST_UTILS
 #  define GR_TEST_UTILS 1
 #endif
 
 #endif // SkPostConfig_DEFINED