Keyboard shortcuts can't be disabled or changed

[garybernhardt]

Steps to reproduce:

1. Open "Extension options" for the Buffer Chrome extension.
2. Change the keyboard shortcut or disable the "Use key shortcut?" checkbox.
3. Scroll down to the save button; it's labeled "Saved" and is grayed out.
4. Close the extension options.
5. Re-open the extension options.

Expected result:

Extension options that I changed were saved and put in effect.

Actual result:

Changes weren't saved and aren't respected. E.g., if I disable the key shortcut, hitting alt-b still opens Buffer on any page. So this isn't just a display bug in the settings UI.