message: fix(compiler): add typings for `COMPILED`.
  Note: This commit has to be synced into G3 again.
diff: * Typings for google closure.
  */
  declare namespace goog {
  + /**
  + * Note: Don't use this to check for advanced compilation,
  + * as it is sometimes true.
  + */
  export const DEBUG: boolean;
  }
  +
  +/**
  + * Use this flag to check for advanced compilation.
  + */
  +declare const COMPILED: boolean;
  