[Omnibox] Remove unused histograms.

[Omnibox] Remove unused histograms.

The histograms removed in this CL are not declared in histograms.xml
and so are not collected at all - removing what is essentially dead
code.

R=sky@chromium.org
BUG=none

Committed: https://crrev.com/15017a9a2aabe274f20c5a719d2763fa166084fc
Cr-Commit-Position: refs/heads/master@{#330153}

[groby-ooo-7-16, 2015-05-15 00:21:12]

Hey Sky, 

it looks like you added those in https://codereview.chromium.org/6679049 with a
"histograms.xml will be fixed later" comment, but I don't see any evidence they
actually were added to histograms.xml

I assume this is safe to remove?

[sky, 2015-05-15 00:53:49]

sky@chromium.org changed reviewers:
+ mpearson@google.com, pkasting@chromium.org
- sky@chromium.org

[sky, 2015-05-15 00:54:23]

Peter or Mark should review this. I added both as I'm not sure if Peter is OOO
today.

[Peter Kasting, 2015-05-15 00:57:09]

Mark is the right reviewer here.

[Mark P, 2015-05-15 18:04:41]

mpearson@chromium.org changed reviewers:
+ mpearson@chromium.org

[Mark P, 2015-05-15 18:04:42]

lgtm

[groby-ooo-7-16, 2015-05-15 18:10:17]

The CQ bit was checked by groby@chromium.org

[commit-bot: I haz the power, 2015-05-15 18:11:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1132333004/20001

[commit-bot: I haz the power, 2015-05-15 18:59:12]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-05-15 19:01:02]

Patchset 2 (id:??) landed as
https://crrev.com/15017a9a2aabe274f20c5a719d2763fa166084fc
Cr-Commit-Position: refs/heads/master@{#330153}