Bug 1352863 - Add a GetPerpendicularDirection() function to DirectionUtils.h. r=kats

MozReview-Commit-ID: KATLVKvXCwI

--HG--
extra : rebase_source : 296db90f4a6376059961232c63ad2d27197fab51

gfx/layers/DirectionUtils.h

@@ -50,6 +50,12 @@ float GetAxisScale(ScrollDirection aDir, const ScaleFactors2D<FromUnits, ToUnits
   }
 }
 
+inline ScrollDirection GetPerpendicularDirection(ScrollDirection aDir) {
+  return aDir == ScrollDirection::HORIZONTAL
+       ? ScrollDirection::VERTICAL
+       : ScrollDirection::HORIZONTAL;
+}
+
 } // namespace layers
 } // namespace mozilla