Added check for ill-conditioned invert

include/core/SkScalar.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 SkScalar_DEFINED
 #define SkScalar_DEFINED
 
@@ skipping 10 matching lines @@
 
 typedef float SkScalar;
 
 #define SK_Scalar1                  1.0f
 #define SK_ScalarHalf               0.5f
 #define SK_ScalarSqrt2              1.41421356f
 #define SK_ScalarPI                 3.14159265f
 #define SK_ScalarTanPIOver8         0.414213562f
 #define SK_ScalarRoot2Over2         0.707106781f
 #define SK_ScalarMax                3.402823466e+38f
+#define SK_ScalarSmallest           1.17549435e-38f
 #define SK_ScalarInfinity           SK_FloatInfinity
 #define SK_ScalarNegativeInfinity   SK_FloatNegativeInfinity
 #define SK_ScalarNaN                SK_FloatNaN
 
 #define SkFixedToScalar(x)          SkFixedToFloat(x)
 #define SkScalarToFixed(x)          SkFloatToFixed(x)
 
 #define SkScalarFloorToScalar(x)    sk_float_floor(x)
 #define SkScalarCeilToScalar(x)     sk_float_ceil(x)
 #define SkScalarRoundToScalar(x)    sk_float_floor((x) + 0.5f)
@@ skipping 23 matching lines @@
 
 typedef double SkScalar;
 
 #define SK_Scalar1                  1.0
 #define SK_ScalarHalf               0.5
 #define SK_ScalarSqrt2              1.414213562373095
 #define SK_ScalarPI                 3.141592653589793
 #define SK_ScalarTanPIOver8         0.4142135623731
 #define SK_ScalarRoot2Over2         0.70710678118655
 #define SK_ScalarMax                1.7976931348623157+308
+#define SK_ScalarSmallest           2.2250738585072014e-308
 #define SK_ScalarInfinity           SK_DoubleInfinity
 #define SK_ScalarNegativeInfinity   SK_DoubleNegativeInfinity
 #define SK_ScalarNaN                SK_DoubleNaN
 
 #define SkFixedToScalar(x)          SkFixedToDouble(x)
 #define SkScalarToFixed(x)          SkDoubleToFixed(x)
 
 #define SkScalarFloorToScalar(x)    floor(x)
 #define SkScalarCeilToScalar(x)     ceil(x)
 #define SkScalarRoundToScalar(x)    floor((x) + 0.5)
@@ skipping 179 matching lines @@
     SkASSERT(n >= 0);
     for (int i = 0; i < n; ++i) {
         if (a[i] != b[i]) {
             return false;
         }
     }
     return true;
 }
 
 #endif