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

ash/tooltips/tooltip_controller.cc

Index: ash/tooltips/tooltip_controller.cc
diff --git a/ash/tooltips/tooltip_controller.cc b/ash/tooltips/tooltip_controller.cc
index 45c4785c081f034c93ce8c86c013bb5c6f1490fa..95c454ec1f53f363ecc9d6dc21e9443145669b6a 100644
--- a/ash/tooltips/tooltip_controller.cc
+++ b/ash/tooltips/tooltip_controller.cc
@@ -452,7 +452,7 @@ void TooltipController::UpdateIfRequired() {
       string16 tooltip_text(tooltip_text_);
       gfx::Point widget_loc = curr_mouse_loc_;
       widget_loc = widget_loc.Add(
-          tooltip_window_->GetBoundsInScreen().origin());
+          tooltip_window_->GetBoundsInScreen().DistanceFromOrigin());

[sky, 2012/10/26 21:37:50]

This feels unnatural. In this case we really want to add two points and use the
resulting point.

[Peter Kasting, 2012/10/26 21:50:12]

I disagree.  The new code seems better.

       GetTooltip()->SetText(tooltip_text, widget_loc);
       GetTooltip()->Show();
       tooltip_shown_timer_.Start(FROM_HERE,