Revert of Allow users to perform queries in the omnibox which begin with a search shortcut.

Revert of Allow users to perform queries in the omnibox which begin with a search shortcut. (patchset #4 id:60001 of https://codereview.chromium.org/477873002/)

Reason for revert:
Caused a few OmniboxViewTest interactive_ui_tests failures (tests need updating too).

build:
http://build.chromium.org/p/chromium.linux/builders/Linux%20Tests/builds/22466

test output:
https://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%281%29/builds/501/steps/interactive_ui_tests/logs/OmniboxViewTest.AcceptKeywordBySpace

Looks like try jobs weren't run, only commit queue earlier. Unsure why commit queue didn't include this test - but it's recommended to run 'git cl try' on patches and review.

Original issue's description:
> Allow users to perform queries in the omnibox which begin with a search
> shortcut.
>
> Previously, if a user had (for example) configured a search shortcut of 'cs' which
> went to cs.chromium.org, they would be unable to (easily) start a query in the
> omnibox starting with 'cs'. Now, backspacing the keyword leaves the space after
> the keyword, allowing the user to continue typing without reenabling keyword
> mode.
>
> BUG=393371
> NOTRY=true
> R=pkasting@chromium.org
> TEST=type 'google.com ' into the omnibar and it should enter keyword mode.
> Press backspace and 'google.com ' will be left in the omnibar, rather than
> 'google.com'.
>
> Committed: https://crrev.com/709649607f13acb04e3850d5fd7fc1903c1becae
> Cr-Commit-Position: refs/heads/master@{#322429}

TBR=pkasting@chromium.org,sky@chromium.org,lenny.khazan@gmail.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=393371
Committed: https://crrev.com/52179c1b310fec1797c81ea9a20326839860b7d3
Cr-Commit-Position: refs/heads/master@{#322448}

[scheib, 2015-03-26 19:30:09]

Created Revert of Allow users to perform queries in the omnibox which begin with
a search shortcut.

[commit-bot: I haz the power, 2015-03-26 19:30:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1030413002/1

[commit-bot: I haz the power, 2015-03-26 19:31:02]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-26 19:31:49]

Patchset 1 (id:??) landed as
https://crrev.com/52179c1b310fec1797c81ea9a20326839860b7d3
Cr-Commit-Position: refs/heads/master@{#322448}