Run browser tests on Atom/Electron

test/browser/language_tests.js

Index: test/browser/language_tests.js
diff --git a/test/browser/language_tests.js b/test/browser/language_tests.js
index 02dc2104c30ed15e67b6039a87f90c83616e3266..2d05cfed8149ff293918b1f9783367f8e9a62fce 100644
--- a/test/browser/language_tests.js
+++ b/test/browser/language_tests.js
@@ -317,14 +317,24 @@
     'no_main_test_01_multi',
   ]);
 
+  let helpers = new Set([
+    'library_prefixes_test1',
+    'library_prefixes_test2',
+    'top_level_prefixed_library_test',
+  ]); 
 
   suite('language', () => {
-    let languageTestPattern = new RegExp('language/(.*_test.*)\\.js');
-    for (let testFile of Object.keys(window.__karma__.files)) {
+    let languageTestPattern = new RegExp('language/(.*_test.*)');
+    for (let testFile of dart_library.libraries()) {
       let match = languageTestPattern.exec(testFile);
       if (match != null) {
         let name = match[1];
 
+        if (helpers.has(name)) {
+          // These are not top-level tests.  They are used by other tests.
+          continue;
+        }
+
         // These two tests are special because they use package:unittest.
         // We run them below.
         if (name == 'async_await_test' || name.startsWith('async_star_test')) {