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

ui/base/gtk/gtk_screen_util.cc

Index: ui/base/gtk/gtk_screen_util.cc
diff --git a/ui/base/gtk/gtk_screen_util.cc b/ui/base/gtk/gtk_screen_util.cc
index f0ef4d35b336cbee3e0c8bb42568a271cb5498d6..718a10a7b95a40f94e8f4d65e5ed42735745998b 100644
--- a/ui/base/gtk/gtk_screen_util.cc
+++ b/ui/base/gtk/gtk_screen_util.cc
@@ -26,12 +26,12 @@ gfx::Point ClientPoint(GtkWidget* widget) {
   return gfx::Point(x, y);
 }
 
-gfx::Point GetWidgetScreenPosition(GtkWidget* widget) {
+gfx::Vector2d GetWidgetScreenOffset(GtkWidget* widget) {
   GdkWindow* window = gtk_widget_get_window(widget);
 
   if (!window) {
     NOTREACHED() << "Must only be called on realized widgets.";
-    return gfx::Point(0, 0);
+    return gfx::Vector2d(0, 0);
   }
 
   gint x, y;
@@ -44,11 +44,11 @@ gfx::Point GetWidgetScreenPosition(GtkWidget* widget) {
     y += allocation.y;
   }
 
-  return gfx::Point(x, y);
+  return gfx::Vector2d(x, y);
 }
 
 gfx::Rect GetWidgetScreenBounds(GtkWidget* widget) {
-  gfx::Point position = GetWidgetScreenPosition(widget);
+  gfx::Point position = PointAtOffsetFromOrigin(GetWidgetScreenOffset(widget));
 
   GtkAllocation allocation;
   gtk_widget_get_allocation(widget, &allocation);