Only CSS references need to traverse

The path adjustment for assets in bundles is only needed with CSS files.  Paths
referenced in JS files are written to elements, where they are relative to the
document.

webpack.config.js

@@ -59,27 +59,28 @@ module.exports = {
                 // lifetime for assets while still delivering changes quickly.
                 oneOf: [
                     {
-                        // Images referenced in HTML files
-                        issuer: /\.html$/,
-                        loader: 'file-loader',
-                        options: {
-                            name: '[name].[hash:7].[ext]',
-                            outputPath: getImgOutputPath,
-                        },
-                    },
-                    {
-                        // Images referenced in JS and CSS files
+                        // Images referenced in CSS files
+                        issuer: /\.(scss|css)$/,
                         loader: 'file-loader',
                         options: {
                             name: '[name].[hash:7].[ext]',
                             outputPath: getImgOutputPath,
                             publicPath: function(url, resourcePath) {
-                                // JS and CSS image usages end up the `bundles/[hash]` output
-                                // directory, so we adjust the final path to navigate up twice.
+                                // CSS image usages end up in the `bundles/[hash]` output
+                                // directory, so we adjust the final path to navigate up
+                                // twice.
                                 return path.join("../..", getImgOutputPath(url, resourcePath));
                             },
                         },
                     },
+                    {
+                        // Images referenced in HTML and JS files
+                        loader: 'file-loader',
+                        options: {
+                            name: '[name].[hash:7].[ext]',
+                            outputPath: getImgOutputPath,
+                        },
+                    },
                 ],
             },
         ],
@@ -193,7 +194,7 @@ module.exports = {
  * @return {string} The returned paths will look like `img/warning.1234567.svg`.
  */
 function getImgOutputPath(url, resourcePath) {
-    const prefix = /^.*\/res\//;
+    const prefix = /^.*[/\\]res[/\\]/;
     const outputDir = path.dirname(resourcePath).replace(prefix, "");
     return path.join(outputDir, path.basename(url));
 }