Stop transpiling karma tests

This runs our code in the same manner as it would be used if loaded
directly in the browser. Includes the same kind of fallback for older
browsers.

tests/karma-test-main.js

@@ -9,8 +9,39 @@ Object.keys(window.__karma__.files).forEach(function (file) {
     }
 });
 
-require.config({
-    baseUrl: '/base',
-    deps: allTestFiles.concat(extraFiles),
-    callback: window.__karma__.start,
+// Stub out mocha's start function so we can run it once we're done loading
+mocha.origRun = mocha.run;
+mocha.run = function () {};
+
+let script;
+
+// Script to import all our tests
+script = document.createElement("script");
+script.type = "module";
+script.text = "";
+let allModules = allTestFiles.concat(extraFiles);
+allModules.forEach(function (file) {
+    script.text += "import \"" + file + "\";\n";
 });
+script.text += "\nmocha.origRun();\n";
+document.body.appendChild(script);
+
+// Fallback code for browsers that don't support modules (IE)
+script = document.createElement("script");
+script.type = "module";
+script.text = "window._noVNC_has_module_support = true;\n";
+document.body.appendChild(script);
+
+function fallback() {
+    if (!window._noVNC_has_module_support) {
+        /* eslint-disable no-console */
+        if (console)
+            console.log("No module support detected. Loading fallback...");
+        /* eslint-enable no-console */
+        let loader = document.createElement("script");
+        loader.src = "base/vendor/browser-es-module-loader/dist/browser-es-module-loader.js";
+        document.body.appendChild(loader);
+    }
+}
+
+setTimeout(fallback, 500);