add test for SkConvertQuadToCubic



git-svn-id: http://skia.googlecode.com/svn/trunk/src@1967 2bbb7eff-a529-9590-31e7-b0007b416f81

diff --git a/core/SkGeometry.cpp b/core/SkGeometry.cpp
index 3c9e9f9..57ce2fd 100644
--- a/core/SkGeometry.cpp
+++ b/core/SkGeometry.cpp

@@ -448,18 +448,20 @@
     }
 }
 
-void SkConvertQuadToCubic(const SkPoint src[3], SkPoint dst[4])
-{
-    SkScalar two = SkIntToScalar(2);
-    SkScalar one_third = SkScalarDiv(SK_Scalar1, SkIntToScalar(3));
-    dst[0].set(src[0].fX, src[0].fY);
-    dst[1].set(
-        SkScalarMul(SkScalarMulAdd(src[1].fX, two, src[0].fX), one_third),
-        SkScalarMul(SkScalarMulAdd(src[1].fY, two, src[0].fY), one_third));
-    dst[2].set(
-        SkScalarMul(SkScalarMulAdd(src[1].fX, two, src[2].fX), one_third),
-        SkScalarMul(SkScalarMulAdd(src[1].fY, two, src[2].fY), one_third));
-    dst[3].set(src[2].fX, src[2].fY);
+#ifdef SK_SCALAR_IS_FLOAT
+    #define SK_ScalarTwoThirds  (0.666666666f)
+#else
+    #define SK_ScalarTwoThirds  ((SkFixed)(43691))
+#endif
+
+void SkConvertQuadToCubic(const SkPoint src[3], SkPoint dst[4]) {
+    const SkScalar scale = SK_ScalarTwoThirds;
+    dst[0] = src[0];
+    dst[1].set(src[0].fX + SkScalarMul(src[1].fX - src[0].fX, scale),
+               src[0].fY + SkScalarMul(src[1].fY - src[0].fY, scale));
+    dst[2].set(src[2].fX + SkScalarMul(src[1].fX - src[2].fX, scale),
+               src[2].fY + SkScalarMul(src[1].fY - src[2].fY, scale));
+    dst[3] = src[2];
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////