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

ui/base/ui_base_types.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_BASE_UI_BASE_TYPES_H_
 #define UI_BASE_UI_BASE_TYPES_H_
 
 #include "ui/base/ui_base_export.h"
 
 namespace ui {
@@ skipping 23 matching lines @@
 // treatments may be handled differently by the window manager.
 enum ModalType {
   MODAL_TYPE_NONE   = 0,  // Window is not modal.
   MODAL_TYPE_WINDOW = 1,  // Window is modal to its transient parent.
   MODAL_TYPE_CHILD  = 2,  // Window is modal to a child of its transient parent.
   MODAL_TYPE_SYSTEM = 3   // Window is modal to all other windows.
 };
 
 // TODO(varunjain): Remove MENU_SOURCE_NONE (crbug.com/250964)
 enum MenuSourceType {
-  MENU_SOURCE_NONE            = 0,
-  MENU_SOURCE_MOUSE           = 1,
-  MENU_SOURCE_KEYBOARD        = 2,
-  MENU_SOURCE_TOUCH           = 3,
-  MENU_SOURCE_TOUCH_EDIT_MENU = 4,
-  MENU_SOURCE_LONG_PRESS      = 5,
-  MENU_SOURCE_LONG_TAP        = 6,
+  MENU_SOURCE_NONE = 0,
+  MENU_SOURCE_MOUSE = 1,
+  MENU_SOURCE_KEYBOARD = 2,
+  MENU_SOURCE_TOUCH = 3,
+  MENU_SOURCE_TOUCH_SIDE_SHELF = 4,

[msw, 2017/05/05 17:34:19]

We probably want to avoid this or make it not shelf-specific (ie. replace
'SHELF' with 'ANCHOR' or 'MENU'); you need to ping ui/base/OWNERS anyway.

+  MENU_SOURCE_TOUCH_EDIT_MENU = 5,
+  MENU_SOURCE_LONG_PRESS = 6,
+  MENU_SOURCE_LONG_TAP = 7,
   MENU_SOURCE_TYPE_LAST = MENU_SOURCE_LONG_TAP
 };
 
 UI_BASE_EXPORT MenuSourceType GetMenuSourceTypeForEvent(const ui::Event& event);
 
 }  // namespace ui
 
 #endif  // UI_BASE_UI_BASE_TYPES_H_