Fix bug in cubic derivative coefficient with missing parens

src/utils/SkCurveMeasure.cpp

Index: src/utils/SkCurveMeasure.cpp
diff --git a/src/utils/SkCurveMeasure.cpp b/src/utils/SkCurveMeasure.cpp
index 60fbf34ff24be9d78085f7333e4a74db0ae2b07b..a38a4fd1f0b99b79fe5544ac11905dbfb12232ed 100644
--- a/src/utils/SkCurveMeasure.cpp
+++ b/src/utils/SkCurveMeasure.cpp
@@ -130,7 +130,7 @@ ArcLengthIntegrator::ArcLengthIntegrator(const SkPoint* pts, SkSegType segType)
             xCoeff[2] = Sk8f(3.0f*(-Ax + Bx));
 
             yCoeff[0] = Sk8f(3.0f*(-Ay + 3.0f*(By - Cy) + Dy));
-            yCoeff[1] = Sk8f(3.0f * -Ay + By + 2.0f*(Ay - 2.0f*By + Cy));
+            yCoeff[1] = Sk8f(3.0f*(2.0f*(Ay - 2.0f*By + Cy)));

[reed1, 2016/08/16 21:19:35]

this seems fine. two nits:

1. don't need 3.0f when 3 will do (I find the latter easier to parse)
2. for efficiency, seems better to resolve some of those constant*
expressions...
    6*(Ay - 2*By + Cy)

             yCoeff[2] = Sk8f(3.0f*(-Ay + By));
         }
             break;