Use whole --message argument on patchset upload

The logic for handling --title, --message, and the
commit message of the most recent commit was accidentally
doing this differently from how Rietveld had done them.

Bug: 728391
Change-Id: I70a46ccb470d790103f5d6bb745902595be28eee
Reviewed-on: https://chromium-review.googlesource.com/527339
Commit-Queue: Aaron Gable <agable@chromium.org>
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>

git_cl.py

@@ -2871,10 +2871,9 @@ class _GerritChangelistImpl(_ChangelistCodereviewBase):
               '%s' % (self.GetIssue(), self.GetIssueURL()))
         if not title:
           if options.message:
-            # For compatibility with Rietveld, if -m|--message is given on
-            # command line, title should be the first line of that message,
-            # which shouldn't be confused with CL description.
-            default_title = options.message.strip().split()[0]
+            # When uploading a subsequent patchset, -m|--message is taken
+            # as the patchset title if --title was not provided.
+            title = options.message.strip()
           else:
             default_title = RunGit(
                 ['show', '-s', '--format=%s', 'HEAD']).strip()