The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e9e6f93ed2bbd520915f9545ec97b2a33211d2ae

commit e9e6f93ed2bbd520915f9545ec97b2a33211d2ae
Author: alshabalin <alshabalin@yandex-team.ru>
Date: Sat Oct 29 06:39:38 2016

Support NSFlagsChanged in ui::EventFromNative.

On Windows and Linux pressing modifier only keys produce key pressed and
key released events but on Mac this wasn't the case. This change adds
support for NSFlagsChanged to equalize.

BUG= 659854 

Review-Url: https://codereview.chromium.org/2439953005
Cr-Commit-Position: refs/heads/master@{#428607}

[modify] https://crrev.com/e9e6f93ed2bbd520915f9545ec97b2a33211d2ae/content/browser/renderer_host/input/web_input_event_builders_mac.mm
[modify] https://crrev.com/e9e6f93ed2bbd520915f9545ec97b2a33211d2ae/ui/events/cocoa/cocoa_event_utils.h
[modify] https://crrev.com/e9e6f93ed2bbd520915f9545ec97b2a33211d2ae/ui/events/cocoa/cocoa_event_utils.mm
[modify] https://crrev.com/e9e6f93ed2bbd520915f9545ec97b2a33211d2ae/ui/events/cocoa/events_mac.mm
[modify] https://crrev.com/e9e6f93ed2bbd520915f9545ec97b2a33211d2ae/ui/events/cocoa/events_mac_unittest.mm
[modify] https://crrev.com/e9e6f93ed2bbd520915f9545ec97b2a33211d2ae/ui/events/test/cocoa_test_event_utils.h
[modify] https://crrev.com/e9e6f93ed2bbd520915f9545ec97b2a33211d2ae/ui/events/test/cocoa_test_event_utils.mm

About handling accelerator-only shortcuts: there seems to be just the 'Alt' key on Windows which focuses the app menu. It follows the Microsoft guideline: https://msdn.microsoft.com/en-us/library/ms971323.aspx#atg_keyboardshortcuts_accessing_menus_and_dialog_boxes
And it's implemented in HWNDMessageHandler::OnSysCommand by converting SC_KEYMENU into VK_MENU accelerator:
https://cs.chromium.org/chromium/src/ui/views/win/hwnd_message_handler.cc?q=hwndmessagehandle&sq=package:chromium&l=2111

Archiving P3s older than 1 year with no owner or component.