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

ash/launcher/overflow_bubble.cc

Index: ash/launcher/overflow_bubble.cc
diff --git a/ash/launcher/overflow_bubble.cc b/ash/launcher/overflow_bubble.cc
index 1161e166b498b6d050cf312a8e7b35f9fdfd4aa4..b123514bb9eceff56fe21c7ae16dcf5fd0b822f1 100644
--- a/ash/launcher/overflow_bubble.cc
+++ b/ash/launcher/overflow_bubble.cc
@@ -84,7 +84,7 @@ class OverflowBubbleView : public views::BubbleDelegateView {
 
   ShelfAlignment shelf_alignment_;
   LauncherView* launcher_view_;  // Owned by views hierarchy.
-  gfx::Point scroll_offset_;
+  gfx::Vector2d scroll_offset_;
 
   DISALLOW_COPY_AND_ASSIGN(OverflowBubbleView);
 };
@@ -166,7 +166,7 @@ gfx::Size OverflowBubbleView::GetPreferredSize() {
 }
 
 void OverflowBubbleView::Layout() {
-  const gfx::Point origin(-scroll_offset_.x(), -scroll_offset_.y());
+  const gfx::Point origin(gfx::PointAtDistanceFromOrigin(-scroll_offset_));
   launcher_view_->SetBoundsRect(gfx::Rect(origin, GetContentsSize()));
 }