Simplify firstdirection

Change-Id: I30d3056dc97a16c08b85fd77120485ef07b18d96
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/314037
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/gm/convex_all_line_paths.cpp b/gm/convex_all_line_paths.cpp
index 3273bda..27f504c 100644
--- a/gm/convex_all_line_paths.cpp
+++ b/gm/convex_all_line_paths.cpp
@@ -258,8 +258,7 @@
         // of the GMs rows.
         SkASSERT(path.isConvex());
         SkASSERT(SkPath::kLine_SegmentMask == path.getSegmentMasks());
-        SkPathFirstDirection actualDir;
-        SkASSERT(SkPathPriv::CheapComputeFirstDirection(path, &actualDir));
+        SkPathFirstDirection actualDir = SkPathPriv::ComputeFirstDirection(path);
         SkASSERT(SkPathPriv::AsFirstDirection(dir) == actualDir);
         SkRect bounds = path.getBounds();
         SkASSERT(SkScalarNearlyEqual(bounds.centerX(), 0.0f));