src/vs/workbench/browser/parts/editor/noTabsTitleControl.ts/NoTabsTitleControl/ifActiveEditorChanged
class NoTabsTitleControl:	private ifActiveEditorChanged(fn: () => void): boolean {
		if (
			!this.activeLabel.editor && this.group.activeEditor || 						// active editor changed from null => editor
			this.activeLabel.editor && !this.group.activeEditor || 						// active editor changed from editor => null
			(!this.activeLabel.editor || !this.group.isActive(this.activeLabel.editor))	// active editor changed from editorA => editorB
		) {
			fn();

			return true;
		}

		return false;
	}