Add stdout param to SubprocessCallAndFilter().

It will eventually replace 'print_messages' and be used to annotate printed
lines when using --jobs.

Review URL: http://codereview.chromium.org/3174020

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@57092 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/gclient.py b/gclient.py
index 4699d1f..cef153e 100644
--- a/gclient.py
+++ b/gclient.py
@@ -1192,6 +1192,8 @@
       options.entries_filename = options.config_filename + '_entries'
       if options.jobs < 1:
         parser.error('--jobs must be 1 or higher')
+      # Useful for --jobs.
+      options.stdout = sys.stdout
 
       # These hacks need to die.
       if not hasattr(options, 'revisions'):