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/delta_diff_generator.cc b/delta_diff_generator.cc
index a500054..f00ac7f 100644
--- a/delta_diff_generator.cc
+++ b/delta_diff_generator.cc
@@ -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.
 
@@ -1553,7 +1553,7 @@
 
   int rc = 1;
   vector<char> patch_file;
-  TEST_AND_RETURN_FALSE(Subprocess::SynchronousExec(cmd, &rc));
+  TEST_AND_RETURN_FALSE(Subprocess::SynchronousExec(cmd, &rc, NULL));
   TEST_AND_RETURN_FALSE(rc == 0);
   TEST_AND_RETURN_FALSE(utils::ReadFile(patch_file_path, out));
   unlink(patch_file_path.c_str());