Add support for --pub-serve.

test/runner/runner_test.dart

Index: test/runner/runner_test.dart
diff --git a/test/runner/runner_test.dart b/test/runner/runner_test.dart
index af67c03590988164b0ae24d3a417721437cb0eab..1c2dc74342423bd38f0c778b5abe1542b2cc830a 100644
--- a/test/runner/runner_test.dart
+++ b/test/runner/runner_test.dart
@@ -37,16 +37,17 @@ void main() {
 final _usage = """
 Usage: pub run test:test [files or directories...]
 
--h, --help          Shows this usage information.
--n, --name          A substring of the name of the test to run.
-                    Regular expression syntax is supported.
+-h, --help                Shows this usage information.
+-n, --name                A substring of the name of the test to run.
+                          Regular expression syntax is supported.
 
--N, --plain-name    A plain-text substring of the name of the test to run.
--p, --platform      The platform(s) on which to run the tests.
-                    [vm (default), chrome]
+-N, --plain-name          A plain-text substring of the name of the test to run.
+-p, --platform            The platform(s) on which to run the tests.
+                          [vm (default), chrome]
 
-    --[no-]color    Whether to use terminal colors.
-                    (auto-detected by default)
+    --pub-serve=<port>    The port of a pub serve instance serving "test/".
+    --[no-]color          Whether to use terminal colors.
+                          (auto-detected by default)
 """;
 
 void main() {