Port SkXfermode opts to SkOpts.h

include/core/SkFloatingPoint.h

Index: include/core/SkFloatingPoint.h
diff --git a/include/core/SkFloatingPoint.h b/include/core/SkFloatingPoint.h
index 2ca1d088d391341eaf1d652353a084a0da7049ba..7427562323f39d3dfe22ea35b37c0c2a382cf0c9 100644
--- a/include/core/SkFloatingPoint.h
+++ b/include/core/SkFloatingPoint.h
@@ -11,7 +11,6 @@
 #define SkFloatingPoint_DEFINED
 
 #include "SkTypes.h"
-#include "../private/SkOpts.h"
 
 #include <math.h>
 #include <float.h>
@@ -128,6 +127,10 @@ extern const uint32_t gIEEENegativeInfinity;
 #define SK_FloatInfinity            (*SkTCast<const float*>(&gIEEEInfinity))
 #define SK_FloatNegativeInfinity    (*SkTCast<const float*>(&gIEEENegativeInfinity))
 
+// We forward declare this to break an #include cycle.
+// (SkScalar -> SkFloatingPoint -> SkOpts.h -> SkXfermode -> SkColor -> SkScalar)
+namespace SkOpts { extern float (*rsqrt)(float); }
+
 // Fast, approximate inverse square root.
 // Compare to name-brand "1.0f / sk_float_sqrt(x)".  Should be around 10x faster on SSE, 2x on NEON.
 static inline float sk_float_rsqrt(const float x) {