Eagerly close browser tests.

test/io.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // TODO(nweiz): Remove this tag when we can get [packageDir] working without it
 // (dart-lang/sdk#24022).
 library test.test.io;
 
 import 'dart:async';
 import 'dart:io';
@@ skipping 78 matching lines @@
 
 /// Returns a [StreamMatcher] that asserts that the stream emits strings
 /// containing each string in [strings] in order.
 ///
 /// This expects each string in [strings] to match a different string in the
 /// stream.
 StreamMatcher containsInOrder(Iterable<String> strings) =>
     inOrder(strings.map((string) => consumeThrough(contains(string))));
 
 /// Runs the test executable with the package root set properly.
+///
+/// If [forwardStdio] is true, the standard output and error from the process
+/// will be printed as part of the parent test. This is used for debugging.
 ScheduledProcess runTest(List args, {String reporter,
-    int concurrency, Map<String, String> environment}) {
+    int concurrency, Map<String, String> environment,
+    bool forwardStdio: false}) {
   reporter ??= "expanded";
   concurrency ??= 1;
 
   var allArgs = [
     p.absolute(p.join(packageDir, 'bin/test.dart')),
     "--package-root=${p.join(packageDir, 'packages')}",
     "--concurrency=$concurrency",
     "--reporter=$reporter"
   ]..addAll(args);
 
   if (environment == null) environment = {};
   environment.putIfAbsent("_UNITTEST_USE_COLOR", () => "false");
 
-  return runDart(allArgs,
+  var process = runDart(allArgs,
       environment: environment,
       description: "dart bin/test.dart");
+
+  if (forwardStdio) {
+    process.stdoutStream().listen(print);
+    process.stderrStream().listen(print);
+  }
+
+  return process;
 }
 
 /// Runs Dart.
 ScheduledProcess runDart(List args, {Map<String, String> environment,
     String description}) {
   var allArgs = Platform.executableArguments.map((arg) {
     // The package root might be relative, so we need to make it absolute if
     // we're going to run in a different working directory.
     if (!arg.startsWith("--package-root=")) return arg;
     return "--package-root=" +
@@ skipping 34 matching lines @@
     var match;
     while (match == null) {
       var line = await pub.stdout.next();
       match = _servingRegExp.firstMatch(line);
     }
     _pubServePortCompleter.complete(int.parse(match[1]));
   }, "waiting for pub serve to emit its port number");
 
   return pub;
 }