Unswap sync backend initialize histograms

Unswap sync backend initialize histograms

This commit also renames the histograms so we can obsolete the old names
and ignore all the stats gathered while the labels were swapped.

BUG=105777
TEST=

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=112257

[rlarocque, 2011-11-29 22:29:14]

Remember http://codereview.chromium.org/8568028?  It turns out that I
accidentally swapped the histogram labels.  This commit fixes that.  

I'll start a separate review for the histograms.xml changes.

[lipalani1, 2011-11-30 00:42:35]

LGTM

[commit-bot: I haz the power, 2011-11-30 00:44:26]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rlarocque@chromium.org/8735007/1

[commit-bot: I haz the power, 2011-11-30 02:56:31]

The commit queue went berserk retrying too often for a
seemingly flaky test. Builder is linux_clang, revision is 112082, job name
was 8735007-1 (previous was lost) (previous was lost) (previous was lost)
(previous was lost).