Steps to reproduce:

1. Open any project with 2017.2.0b1
2. Open some window that is not in the 'Windows' menu tab, e.g. 'Build Settings', 'Preferences', 'Module Manager', etc.
3. Focus it and try to close it using CMD+W key shortcut

Expected behaviour: The window closes
Actual behaviour: Window ignores the shortcut and stays open

Notes:
Not sure if such shortcut exists on Windows, if so, could be reproducible there as well.
All editor windows from the 'Window' menu tab react to the CMD+W as they used to: when the window is detached - it closes, when the window is docked to the editor - the command gets ignored.

Reproduced with: 2017.2.0b1
Doesn't reproduce with: 2017.1.0f1