Minor history tweaks that I came across while looking at crashes.

Minor history tweaks that I came across while looking at crashes.
. Make HistoryService::Cleanup() private. Making this public can leave
  HistoryService in a bad state.
. HistoryServiceFactory would leak a HistoryService if
  HistoryService::Init() failed.

BUG=none
TEST=none
R=brettw@chromium.org

Committed: https://crrev.com/2d5a858de159092b39950df50c46aafb876e6b56
Cr-Commit-Position: refs/heads/master@{#292382}

[sky, 2014-08-27 23:59:02]

sky@chromium.org changed reviewers:
+ brettw@chromium.org
- brettw@chromium.orgt

[sky, 2014-08-27 23:59:12]

This time with the right reviewer.

[brettw, 2014-08-28 04:50:22]

lgtm

[sky, 2014-08-28 13:08:54]

The CQ bit was checked by sky@chromium.org

[commit-bot: I haz the power, 2014-08-28 13:09:20]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/sky@chromium.org/510033004/1

[commit-bot: I haz the power, 2014-08-28 14:03:00]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  android_dbg_tests_recipe on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/android_dbg_tes...)
  mac_chromium_compile_dbg on tryserver.chromium.mac
(http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_comp...)

[commit-bot: I haz the power, 2014-08-28 14:56:06]

Committed patchset #1 (id:1) as bcfedb750dbb567f4894419db807cc9f5486e019

[commit-bot: I haz the power, 2014-09-10 02:59:34]

Patchset 1 (id:??) landed as
https://crrev.com/2d5a858de159092b39950df50c46aafb876e6b56
Cr-Commit-Position: refs/heads/master@{#292382}