Correct SkFixedToDouble.

include/core/SkFixed.h

Index: include/core/SkFixed.h
diff --git a/include/core/SkFixed.h b/include/core/SkFixed.h
index 8cf7a5679ce28358e994114204aba92162bc4332..f143eab51e86842553abd100a5b00aa601cba4dd 100644
--- a/include/core/SkFixed.h
+++ b/include/core/SkFixed.h
@@ -28,7 +28,7 @@ typedef int32_t             SkFixed;
 #define SK_FixedTanPIOver8  (0x6A0A)
 #define SK_FixedRoot2Over2  (0xB505)
 
-#define SkFixedToFloat(x)   ((x) * 1.5258789e-5f)
+#define SkFixedToFloat(x)   ((x) * 1.52587890e-5f)

[bungeman-skia, 2015/04/16 20:41:31]

Note that 1.8 is needed to correctly round trip float, and 1.16 is needed to
correctly round trip double.

This value is wrong, as 1.52587891e-5f is more correct (rounded, what %1.8f
would actually produce). For constants like this, C++ doesn't specify which
rounding rule to use, and various compilers are actually different.
1.52587890e-5f can round down depending. 1.52587891e-5f always maps to the
correct value without issue. However, 1.52587890625e-5 is obvious, exact in
decimal, and is correct. So just do that.

 #if 1
     #define SkFloatToFixed(x)   ((SkFixed)((x) * SK_Fixed1))
 #else
@@ -50,7 +50,7 @@ typedef int32_t             SkFixed;
     #define SkFloatToFixed_Check(x) SkFloatToFixed(x)
 #endif
 
-#define SkFixedToDouble(x)  ((x) * 1.5258789e-5)
+#define SkFixedToDouble(x)  ((x) * 1.52587890625e-5)
 #define SkDoubleToFixed(x)  ((SkFixed)((x) * SK_Fixed1))
 
 /** Converts an integer to a SkFixed, asserting that the result does not overflow