Handle errors in posting sync commit messages

Handle errors in posting sync commit messages

This fixes an oversight in r117285.  That commit should have included
these changes, but the diffs were accidentally misplaced.

Prior to this commit, all PostCommitMessage tasks would seem to have
succeeded.  However, this bug did not affect the return values from
ProcessCommitResponseCommand, so the syncer should be able to detect
commit failures even without this fix.

BUG=117893
TEST=


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=126701

[rlarocque, 2012-03-12 22:27:16]

Fixes an issue resulting from bad diff management when fixing
SYNC_CYCLE_CONTINUATION errors.  See http://codereview.chromium.org/9158004.

Please review.

[tim (not reviewing), 2012-03-13 00:40:52]

LGTM

[commit-bot: I haz the power, 2012-03-13 17:52:43]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rlarocque@chromium.org/9695016/1

[commit-bot: I haz the power, 2012-03-13 20:29:28]

Try job failure for 9695016-1 (retry) on win_rel for step "browser_tests".
It's a second try, previously, steps "browser_tests, installer_util_unittests"
failed.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[commit-bot: I haz the power, 2012-03-13 20:33:47]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rlarocque@chromium.org/9695016/1

[commit-bot: I haz the power, 2012-03-13 23:53:04]

Try job failure for 9695016-1 (previous was lost) (retry) on win_rel for step
"browser_tests".
It's a second try, previously, step "browser_tests" failed.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[commit-bot: I haz the power, 2012-03-14 17:57:22]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rlarocque@chromium.org/9695016/1

[commit-bot: I haz the power, 2012-03-14 19:15:59]

Change committed as 126701