code: function compile(srcs, out, args) {
    // Get the compiler arguments, using the defaults if not specified.
    const combinedArgs = Object.assign({}, COMPILER_DEFAULT_ARGS, args);
    return gulp
        .src(srcs)
        .pipe(closureCompiler({
          compilerPath: COMPILER_PATH,
          fileName: path.basename(out),
          compilerFlags: combinedArgs
        }))
        .pipe(gulp.dest(path.dirname(out)));
  }
docs: Invokes Closure Compiler.
  @param {!Array<string>} srcs The JS sources to compile.
  @param {string} out The path to the output JS file.
  @param {!Object} args Additional arguments to Closure compiler.
  @return {*} A stream that finishes when compliation finishes.