src/vs/editor/common/config/editorOptions.ts/EditorAccessibilitySupport/validate
class EditorAccessibilitySupport:	public validate(input: any): AccessibilitySupport {
		switch (input) {
			case 'auto': return AccessibilitySupport.Unknown;
			case 'off': return AccessibilitySupport.Disabled;
			case 'on': return AccessibilitySupport.Enabled;
		}
		return this.defaultValue;
	}