fix cubic linear test

src/pathops/SkPathOpsCubic.cpp

Index: src/pathops/SkPathOpsCubic.cpp
diff --git a/src/pathops/SkPathOpsCubic.cpp b/src/pathops/SkPathOpsCubic.cpp
index 6fcb348e4ff8fdad349989e9ca218ea70437bbcd..bdae492de07b65a0ff4136a4ff25a78787544ae3 100644
--- a/src/pathops/SkPathOpsCubic.cpp
+++ b/src/pathops/SkPathOpsCubic.cpp
@@ -212,6 +212,9 @@ bool SkDCubic::hullIntersects(const SkDConic& conic, bool* isLinear) const {
 }
 
 bool SkDCubic::isLinear(int startIndex, int endIndex) const {
+    if (fPts[0].approximatelyDEqual(fPts[3]))  {
+        return ((const SkDQuad *) this)->isLinear(0, 2);
+    }
     SkLineParameters lineParameters;
     lineParameters.cubicEndPoints(*this, startIndex, endIndex);
     // FIXME: maybe it's possible to avoid this and compare non-normalized