Add a drop shadow to the fullscreen exit bubble on windows.

ui/views/bubble/bubble_border.h

Index: ui/views/bubble/bubble_border.h
diff --git a/ui/views/bubble/bubble_border.h b/ui/views/bubble/bubble_border.h
index 09e20bb5ad2d7573695503cdf34e74e47a2650cb..c6fa341e8a62e2b50239e0154f1f0c2c52a2cb12 100644
--- a/ui/views/bubble/bubble_border.h
+++ b/ui/views/bubble/bubble_border.h
@@ -115,6 +115,9 @@ class VIEWS_EXPORT BubbleBorder : public views::Border {
   // Overridden from views::Border:
   virtual void GetInsets(gfx::Insets* insets) const;
 
+  // How many pixels the bubble border is from the edge of the images.
+  int pixels_to_border() const;
+
  private:
   struct BorderImages;