Make Dart heap size bigger when running pub.

sdk/lib/_internal/pub/test/test_pub.dart

Index: sdk/lib/_internal/pub/test/test_pub.dart
diff --git a/sdk/lib/_internal/pub/test/test_pub.dart b/sdk/lib/_internal/pub/test/test_pub.dart
index 5da6eb62a3931ad7435b5e88d96068faea8fda38..220674da75f238039c8dca9de9443d5a465569d0 100644
--- a/sdk/lib/_internal/pub/test/test_pub.dart
+++ b/sdk/lib/_internal/pub/test/test_pub.dart
@@ -472,8 +472,12 @@ ScheduledProcess startPub({List args, Future<Uri> tokenEndpoint}) {
   // Find the main pub entrypoint.
   var pubPath = path.join(testDirectory, '..', 'bin', 'pub.dart');
 
-  var dartArgs = ['--package-root=$_packageRoot/', '--checked', pubPath,
-      '--verbose'];
+  var dartArgs = [
+    '--package-root=$_packageRoot/',
+    // Make the heap bigger since dart2js uses a lot of memory.
+    '--new_gen_heap_size=256', '--old_gen_heap_size=1536',
+    '--checked', pubPath, '--verbose'
+  ];
   dartArgs.addAll(args);
 
   if (tokenEndpoint == null) tokenEndpoint = new Future.value();