Move browser tests that require installation into their own files.

test/runner/signal_test.dart

Index: test/runner/signal_test.dart
diff --git a/test/runner/signal_test.dart b/test/runner/signal_test.dart
index 81fbbb5b4cd3dc12d4936f2aaa795d028bc7c278..ffb2de5be7a673ba6097cad31301e89089b02c82 100644
--- a/test/runner/signal_test.dart
+++ b/test/runner/signal_test.dart
@@ -147,7 +147,7 @@ void main() {
 }
 """);
 
-      return _startTest(["-p", "chrome", "test.dart"]).then((process) {
+      return _startTest(["-p", "content-shell", "test.dart"]).then((process) {
         return _lines.bind(process.stdout).skip(3).first.then((line) {
           expect(line, equals("running test"));
           process.kill();