Cleanup usage of history namespace in components/history

Cleanup usage of history namespace in components/history

Move PageUsageData from the global namespace to the history namespace,
fix forward-declarations, removing old unused ones.

Remove unnecessary history:: prefix to refer to names in the history
namespace from the code in the history namespace itself.

Move anonymous namespace in implementation files as sub-namespace of
the history namespace so that they can refer to name in history without
using the history:: prefix.

BUG=None
TBR=dbeam@chromium.org
TBR=jhawkins@chromium.org

Committed: https://crrev.com/dfd044a845d0950b41b70c62aba0d174ef4b8c1a
Cr-Commit-Position: refs/heads/master@{#315003}

[sdefresne, 2015-02-05 15:45:41]

sdefresne@chromium.org changed reviewers:
+ droger@chromium.org

[sdefresne, 2015-02-05 15:45:41]

Please take a look.

[droger, 2015-02-05 16:09:45]

lgtm

[sdefresne, 2015-02-06 10:39:09]

sdefresne@chromium.org changed reviewers:
+ dbeam@chromium.org, jhawkins@chromium.org

[sdefresne, 2015-02-06 10:40:00]

TBR-ing OWNERS of impacted code since changes are mechanical

dbeam for //chrome/browser/ui/webui
jhawkins for //chrome/browser/jumplist_win.h and //chrome/browser/ui/cocoa

[sdefresne, 2015-02-06 10:40:03]

The CQ bit was checked by sdefresne@chromium.org

[commit-bot: I haz the power, 2015-02-06 10:41:09]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/896093004/1

[commit-bot: I haz the power, 2015-02-06 12:12:28]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-06 12:13:49]

Patchset 1 (id:??) landed as
https://crrev.com/dfd044a845d0950b41b70c62aba0d174ef4b8c1a
Cr-Commit-Position: refs/heads/master@{#315003}

[James Hawkins, 2015-02-06 15:12:34]

lgtm