fix(build): added autoprefixer to prod

Fix #3156
Close #3164

Author: grizzm0

packages/angular-cli/models/webpack-build-common.ts

@@ -6,8 +6,6 @@ import {BaseHrefWebpackPlugin} from '@angular-cli/base-href-webpack';
 
 const ProgressPlugin  = require('webpack/lib/ProgressPlugin');
 const HtmlWebpackPlugin = require('html-webpack-plugin');
-const autoprefixer = require('autoprefixer');
-
 
 export function getWebpackCommonConfig(
   projectRoot: string,
@@ -138,7 +136,9 @@ export function getWebpackCommonConfig(
       new webpack.LoaderOptionsPlugin({
         test: /\.(css|scss|sass|less|styl)$/,
         options: {
-          postcss: [ autoprefixer() ]
+          postcss: [
+            require('autoprefixer')
+          ]
         },
       })
     ].concat(extraPlugins),

packages/angular-cli/models/webpack-build-production.ts

@@ -71,8 +71,10 @@ export const getWebpackProdConfigPartial = function(projectRoot: string,
           threshold: 10240
       }),
       new webpack.LoaderOptionsPlugin({
+        test: /\.(css|scss|sass|less|styl)$/,
         options: {
           postcss: [
+            require('autoprefixer'),
             require('postcss-discard-comments')
           ]
         }