ubsan shift fixes

src/core/SkScan_Path.cpp

Index: src/core/SkScan_Path.cpp
diff --git a/src/core/SkScan_Path.cpp b/src/core/SkScan_Path.cpp
index fc79fc8537d08fdbff306ee801a2fa66a5a9a6a2..30a7c576598d56df96757bda6257dbba0f1e3301 100644
--- a/src/core/SkScan_Path.cpp
+++ b/src/core/SkScan_Path.cpp
@@ -450,8 +450,8 @@ void sk_fill_path(const SkPath& path, const SkIRect* clipRect, SkBlitter* blitte
 
     // now edge is the head of the sorted linklist
 
-    start_y <<= shiftEdgesUp;
-    stop_y <<= shiftEdgesUp;
+    start_y = SkLeftShift(start_y, shiftEdgesUp);
+    stop_y = SkLeftShift(stop_y, shiftEdgesUp);
     if (clipRect && start_y < clipRect->fTop) {
         start_y = clipRect->fTop;
     }