AU: Add support for reading the output of synchronous exec calls.

This will be used in a subsequent patch to invoke 'crossystem hwid' to read the
HWID.

BUG=chromium-os:15255
TEST=unit tests, tested AU on device

Change-Id: Ie26bae3621626d40f92f08e8549eefda77151102
Reviewed-on: http://gerrit.chromium.org/gerrit/1047
Reviewed-by: Thieu Le <thieule@chromium.org>
Tested-by: Darin Petkov <petkov@chromium.org>
diff --git a/test_utils.h b/test_utils.h
index 2283e6a..b5ac853 100644
--- a/test_utils.h
+++ b/test_utils.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+// Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
@@ -121,7 +121,7 @@
       args.push_back("-d");
       args.push_back(dev_);
       int return_code = 0;
-      EXPECT_TRUE(Subprocess::SynchronousExec(args, &return_code));
+      EXPECT_TRUE(Subprocess::SynchronousExec(args, &return_code, NULL));
       if (return_code == 0) {
         return;
       }