Add Vector2d classes that represent offsets, instead of using Point.

ui/aura/test/event_generator.cc

Index: ui/aura/test/event_generator.cc
diff --git a/ui/aura/test/event_generator.cc b/ui/aura/test/event_generator.cc
index a2eb897daad5d2853beaaa66c9ad3e9699591ca8..57cf5b6f76ba61c51ed424f2e671a597ec84bdf1 100644
--- a/ui/aura/test/event_generator.cc
+++ b/ui/aura/test/event_generator.cc
@@ -126,10 +126,10 @@ void EventGenerator::MoveMouseTo(const gfx::Point& point, int count) {
   DCHECK_GT(count, 0);
   const ui::EventType event_type = (flags_ & ui::EF_LEFT_MOUSE_BUTTON) ?
       ui::ET_MOUSE_DRAGGED : ui::ET_MOUSE_MOVED;
-  const gfx::Point diff = point.Subtract(current_location_);
+  const gfx::Vector2d diff = point.DistanceFrom(current_location_);
   for (int i = 1; i <= count; i++) {
     const gfx::Point move_point = current_location_.Add(
-        gfx::Point(diff.x() / count * i, diff.y() / count * i));
+        gfx::Vector2d(diff.x() / count * i, diff.y() / count * i));
     ui::MouseEvent mouseev(event_type, move_point, move_point, flags_);
     Dispatch(mouseev);
   }