Align the base of the shelf's context menu to the top edge of the shelf.

ui/views/controls/menu/menu_types.h

Index: ui/views/controls/menu/menu_types.h
diff --git a/ui/views/controls/menu/menu_types.h b/ui/views/controls/menu/menu_types.h
index 160dd5ae3d1f9c5b4a9e3304511234f1931dc909..2f9922261f5441f8e93f5f993bc7dea2dd16ac7c 100644
--- a/ui/views/controls/menu/menu_types.h
+++ b/ui/views/controls/menu/menu_types.h
@@ -10,11 +10,14 @@ namespace views {
 // Where a popup menu should be anchored to for non-RTL languages. The opposite
 // position will be used if base::i18n:IsRTL() is true. The BUBBLE flags are
 // used when the menu should get enclosed by a bubble. Note that BUBBLE flags
-// should only be used with menus which have no children.
+// should only be used with menus which have no children. The Fixed flags are
+// used for the menus that have a fixed anchor position.
 enum MenuAnchorPosition {
   MENU_ANCHOR_TOPLEFT,
   MENU_ANCHOR_TOPRIGHT,
   MENU_ANCHOR_BOTTOMCENTER,
+  MENU_ANCHOR_FIXED_BOTTOMCENTER,
+  MENU_ANCHOR_FIXED_SIDECENTER,
   MENU_ANCHOR_BUBBLE_LEFT,
   MENU_ANCHOR_BUBBLE_RIGHT,
   MENU_ANCHOR_BUBBLE_ABOVE,