change hairline procs to take SkPoint by value, more efficient on SSE and NEON

src/core/SkScan_Antihair.cpp

Index: src/core/SkScan_Antihair.cpp
diff --git a/src/core/SkScan_Antihair.cpp b/src/core/SkScan_Antihair.cpp
index 97bb6d21989bfd86b6e30e079e09e05492cda2e3..c48ad2c3f4246f46b6abfeb9414149fab76af828 100644
--- a/src/core/SkScan_Antihair.cpp
+++ b/src/core/SkScan_Antihair.cpp
@@ -588,8 +588,7 @@ static void do_anti_hairline(SkFDot6 x0, SkFDot6 y0, SkFDot6 x1, SkFDot6 y1,
     }
 }
 
-void SkScan::AntiHairLineRgn(const SkPoint& pt0, const SkPoint& pt1,
-                             const SkRegion* clip, SkBlitter* blitter) {
+void SkScan::AntiHairLineRgn(SkPoint pt0, SkPoint pt1, const SkRegion* clip, SkBlitter* blitter) {
     if (clip && clip->isEmpty()) {
         return;
     }