This is very confusing as seen in #12974 or #12906. My suggestion would be "legacy."
*/
"use strict";
var autoprefixer = require("autoprefixer");
var calc = require("postcss-calc");
var fs = require("fs");
var gulp = require("gulp");
var postcss = require("gulp-postcss");
var rename = require("gulp-rename");
var replace = require("gulp-replace");
var mkdirp = require("mkdirp");
var path = require("path");
var rimraf = require("rimraf");
var stream = require("stream");
var exec = require("child_process").exec;
var spawn = require("child_process").spawn;
var spawnSync = require("child_process").spawnSync;
var streamqueue = require("streamqueue");
var merge = require("merge-stream");
var zip = require("gulp-zip");
var webpack2 = require("webpack");
var webpackStream = require("webpack-stream");
var Vinyl = require("vinyl");
var vfs = require("vinyl-fs");
var through = require("through2");
var BUILD_DIR = "build/";
var L10N_DIR = "l10n/";
var TEST_DIR = "test/";
var EXTENSION_SRC_DIR = "extensions/";
var BASELINE_DIR = BUILD_DIR + "baseline/";
var MOZCENTRAL_BASELINE_DIR = BUILD_DIR + "mozcentral.baseline/";