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

ui/views/controls/menu/menu_runner.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_VIEWS_CONTROLS_MENU_MENU_RUNNER_H_
 #define UI_VIEWS_CONTROLS_MENU_MENU_RUNNER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 67 matching lines @@
 
     // The menu should behave like a Windows native Combobox dropdow menu.
     // This behavior includes accepting the pending item and closing on F4.
     COMBOBOX = 1 << 4,
 
     // A child view is performing a drag-and-drop operation, so the menu should
     // stay open (even if it doesn't receive drag updated events). In this case,
     // the caller is responsible for closing the menu upon completion of the
     // drag-and-drop.
     NESTED_DRAG = 1 << 5,
+
+    // The context menu of the shelf item.
+    SHELF_CONTEXT_MENU = 1 << 6,

[sadrul, 2017/05/10 01:25:40]

Can you call this FIXED_ANCHOR, or something like that? Essentially, it's a hint
to MenuRunner so that it does not attempt to figure out the anchor-position by
itself. Because views should not need to know about 'shelf' etc.

   };
 
   // Creates a new MenuRunner, which may use a native menu if available.
   // |run_types| is a bitmask of RunTypes. If provided,
   // |on_menu_closed_callback| is invoked when the menu is closed.
   // Note that with a native menu (e.g. on Mac), the ASYNC flag in |run_types|
   // may be ignored. See http://crbug.com/682544.
   MenuRunner(ui::MenuModel* menu_model,
              int32_t run_types,
              const base::Closure& on_menu_closed_callback = base::Closure());
@@ skipping 56 matching lines @@
 
  protected:
   DisplayChangeListener() {}
 };
 
 }  // namespace internal
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_MENU_MENU_RUNNER_H_