Add a LoadSuite class.

test/runner/browser/firefox_test.dart

Index: test/runner/browser/firefox_test.dart
diff --git a/test/runner/browser/firefox_test.dart b/test/runner/browser/firefox_test.dart
index 3cf997187ed50543a8fcd171ec6a6a8a775a206b..4539641dfccddd650ced2e4787740ac8da26a36d 100644
--- a/test/runner/browser/firefox_test.dart
+++ b/test/runner/browser/firefox_test.dart
@@ -175,7 +175,10 @@ void main() {
 
     test("alongside another browser", () {
       var result = _runTest(["-p", "firefox", "-p", "chrome", "test.dart"]);
-      expect("Compiling".allMatches(result.stdout), hasLength(1));
+
+      // Only one browser should compile the code.
+      expect(result.stdout.contains("[Chrome] compiling"),
+          isNot(result.stdout.contains("[Firefox] compiling")));
       expect(result.exitCode, equals(0));
     });
   });