Bug 1616386 - Fix Quaternion copy constructor r=lsalzman

Fix Quaternion copy constructor

Differential Revision: https://phabricator.services.mozilla.com/D63255

--HG--
extra : moz-landing-system : lando

gfx/2d/Quaternion.h

@@ -28,7 +28,7 @@ class BaseQuaternion {
   BaseQuaternion(const BaseQuaternion& aOther) {
     x = aOther.x;
     y = aOther.y;
-    z = aOther.y;
+    z = aOther.z;
     w = aOther.w;
   }