[API] Implement register/unregister global desktop keyboard shortcut on Winodws.

- Introduce GlobalShortcutListener;
- New api object: Shortcut({'key': '...', 'active': ..., 'failed': ...});
- New api: App.registerGlobalHotkey, App.unregisterGlobalHotkey.
[Test] Manual test case for global keyboard shortcut.
[API] Finish register global desktop keyboard shortcut on linux.
[Test] Automatic test case for keyboard shortcut.
Remove DCHECK limitation of GlobalShortcutListener.
[API] Finish register global desktop keyboard shortcut on OSX.
Improvement: |key| of |Shortcut| should be case-insensitive.
Address comment: change {un}registerGlobalHotKey to sync method.
Fix build error of missing parameter: isolate.
X11ErrorTracker has been moved "ui/gfx/x/".
Merge pull request #1735 from zhchbin/hotkey

[API] Implement register/unregister global desktop keyboard shortcut.