Revert of Store default search provider data in dictionary pref.

Revert of Store default search provider data in dictionary pref. (https://codereview.chromium.org/229763005/)

Reason for revert:
Speculative revert for introducing lots of leaks. See: http://build.chromium.org/p/chromium.memory/builders/Linux%20ASan%20LSan%20Tests%20%282%29/builds/2026

Original issue's description:
> Store default search provider data in dictionary pref, and add DefaultSearchManager class to handle the reading and writing of this pref (DefaultSearchManager will eventually all default search related concerns).
> 
> This pref will be used to persist data about user-selected 
> default search providers. In future CLs, support will be added for default search providers set by policy and sync.
> 
> 
> BUG=365762
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=266479

BUG=365762
TBR=gab, erikwright, Peter Kasting, Cait Phillips
NOTREECHECKS=true
NOTRY=true

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=266559

[Michael Achenbach, 2014-04-28 13:58:54]

Created Revert of Store default search provider data in dictionary pref.

[commit-bot: I haz the power, 2014-04-28 14:01:56]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/machenbach@chromium.org/258933009/1

[commit-bot: I haz the power, 2014-04-28 14:01:57]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-04-28 14:01:58]

No LGTM from a valid reviewer yet. Only full committers are accepted.
Even if an LGTM may have been provided, it was from a non-committer or
a lowly provisional committer, _not_ a full super star committer.
See http://www.chromium.org/getting-involved/become-a-committer
Note that this has nothing to do with OWNERS files.

[Michael Achenbach, 2014-04-28 14:06:24]

The CQ bit was checked by machenbach@chromium.org

[commit-bot: I haz the power, 2014-04-28 14:07:21]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/machenbach@chromium.org/258933009/1

[commit-bot: I haz the power, 2014-04-28 14:17:37]

Change committed as 266559