Cut the comment short in Rietveld.add_comment(). [follow up of r177704]

Very long comments, like when posting a diff that failed to apply, cause extra
burden on the Commit Queue logs.

TBR=csharp@chromium.org
BUG=


Review URL: https://chromiumcodereview.appspot.com/11929027

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@177713 0039d316-1c4b-4281-b951-d872f2087c98

rietveld.py

@@ -246,7 +246,7 @@ class Rietveld(object):
     tail = '…\n(message too large)'
     if len(message) > max_message:
       message = message[:max_message-len(tail)] + tail
-    logging.info('issue %d; comment: %s' % (issue, message.strip()))
+    logging.info('issue %d; comment: %s' % (issue, message.strip()[:300]))
     return self.post('/%d/publish' % issue, [
         ('xsrf_token', self.xsrf_token()),
         ('message', message),