perf(css): reenable MergeLonghand CSS optimization

The original issue was fixed in cssnano/cssnano#652
so it's safe to reenable this optimization

Author: manucorporat

package.json

@@ -80,7 +80,7 @@
     "autoprefixer": "9.4.3",
     "conventional-changelog-cli": "^1.3.5",
     "css-what": "2.1.0",
-    "cssnano": "4.1.7",
+    "cssnano": "4.1.8",
     "estree-walker": "0.5.2",
     "execa": "^0.8.0",
     "exit": "^0.1.2",
@@ -102,7 +102,7 @@
     "opn": "5.4.0",
     "parse5": "5.1.0",
     "pixelmatch": "4.0.2",
-    "postcss": "7.0.7",
+    "postcss": "7.0.11",
     "puppeteer": "~1.7.0",
     "rollup": "0.68.2",
     "rollup-plugin-commonjs": "9.2.0",

scripts/helpers/cssnano-preset-default.js

@@ -27,7 +27,7 @@ const postcssMinifyParams = require('postcss-minify-params');
 // const postcssNormalizeCharset = require('postcss-normalize-charset');
 const postcssMinifyFontValues = require('postcss-minify-font-values');
 const postcssNormalizeUrl = require('postcss-normalize-url');
-// const postcssMergeLonghand = require('postcss-merge-longhand');
+const postcssMergeLonghand = require('postcss-merge-longhand');
 const postcssDiscardDuplicates = require('postcss-discard-duplicates');
 // const postcssDiscardOverridden = require('postcss-discard-overridden');
 const postcssNormalizeRepeatStyle = require('postcss-normalize-repeat-style');
@@ -80,7 +80,7 @@ module.exports = function defaultPreset (opts = {}) {
     [postcssNormalizeRepeatStyle, options.normalizeRepeatStyle],
     [postcssNormalizePositions, options.normalizePositions],
     [postcssNormalizeWhitespace, options.normalizeWhitespace],
-    // [postcssMergeLonghand, options.mergeLonghand],
+    [postcssMergeLonghand, options.mergeLonghand],
     [postcssDiscardDuplicates, options.discardDuplicates],
     [postcssMergeRules, options.mergeRules],
     [postcssDiscardEmpty, options.discardEmpty],