fix(karma-webpack): dont include the os.tmpdir in the webpack public path

Author: pat841

src/karma-webpack.js

@@ -69,7 +69,7 @@ function Plugin(
     // Must have the common _karma_webpack_ prefix on path here to avoid
     // https://github.com/webpack/webpack/issues/645
     webpackOptions.output.path = path.join(os.tmpdir(), '_karma_webpack_', indexPath, '/')
-    webpackOptions.output.publicPath = path.join(os.tmpdir(), '_karma_webpack_', publicPath, '/')
+    webpackOptions.output.publicPath = path.join('/_karma_webpack_', publicPath, '/')
     webpackOptions.output.filename = '[name]'
     if (includeIndex) {
       webpackOptions.output.jsonpFunction = `webpackJsonp${index}`
@@ -197,7 +197,7 @@ function Plugin(
     compiler.plugin('invalid', invalid.bind(this))
   }
 
-  webpackMiddlewareOptions.publicPath = path.join(os.tmpdir(), '_karma_webpack_', '/')
+  webpackMiddlewareOptions.publicPath = '/_karma_webpack_/'
   var middleware = this.middleware = new webpackDevMiddleware(compiler, webpackMiddlewareOptions)
 
   customFileHandlers.push({