Use float rather than SkFixed for gradient TileProcs.

src/effects/gradients/SkTwoPointConicalGradient.h

Index: src/effects/gradients/SkTwoPointConicalGradient.h
diff --git a/src/effects/gradients/SkTwoPointConicalGradient.h b/src/effects/gradients/SkTwoPointConicalGradient.h
index 5783c39bd4769e7274064fd086ec02311d69430d..11f1afe8a26fd15ec147296fbfcf3dc8b7b99344 100644
--- a/src/effects/gradients/SkTwoPointConicalGradient.h
+++ b/src/effects/gradients/SkTwoPointConicalGradient.h
@@ -9,15 +9,14 @@
 #ifndef SkTwoPointConicalGradient_DEFINED
 #define SkTwoPointConicalGradient_DEFINED
 
+#include "math.h"
+
 #include "SkGradientShaderPriv.h"
 
 // TODO(dominikg): Worth making it truly immutable (i.e. set values in constructor)?
 // Should only be initialized once via init(). Immutable afterwards.
 struct TwoPtRadial {
-    enum {
-        // This value is outside the range SK_FixedMin to SK_FixedMax.
-        kDontDrawT  = 0x80000000
-    };
+    static const float kDontDrawT;
 
     float   fCenterX, fCenterY;
     float   fDCenterX, fDCenterY;
@@ -32,8 +31,8 @@ struct TwoPtRadial {
               const SkPoint& center1, SkScalar rad1,
               bool flipped);
 
-    static bool DontDrawT(SkFixed t) {
-        return kDontDrawT == (uint32_t)t;
+    static bool DontDrawT(float t) {
+        return isnan(t);
     }
 };