src/vs/editor/browser/config/migrateOptions.ts/EditorSettingMigration/apply
class EditorSettingMigration:	apply(options: any): void {
		const value = EditorSettingMigration._read(options, this.key);
		const read = (key: string) => EditorSettingMigration._read(options, key);
		const write = (key: string, value: any) => EditorSettingMigration._write(options, key, value);
		this.migrate(value, read, write);
	}