Revert of components: Make user_prefs a source_set.

Revert of components: Make user_prefs a source_set. (patchset #1 id:1 of https://codereview.chromium.org/1258653002/)

Reason for revert:
Try to fix UserPrefs::Get() crashes.

Original issue's description:
> components: Make user_prefs a source_set.
>
> This is a tiny component, it does not need to be a shared libray in the
> component build.
>
> BUG=None
> R=brettw@chromium.org
>
> Committed: https://crrev.com/f8a72db8313967a512ea94c05b3951c255a4b796
> Cr-Commit-Position: refs/heads/master@{#340349}

TBR=brettw@chromium.org,tfarina@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=None

Committed: https://crrev.com/40f883687274257f05d2f933602318fcc6a5ed7f
Cr-Commit-Position: refs/heads/master@{#340401}

[dcheng, 2015-07-25 05:22:27]

Created Revert of components: Make user_prefs a source_set.

[commit-bot: I haz the power, 2015-07-25 05:22:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1254123002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1254123002/1

[commit-bot: I haz the power, 2015-07-25 05:22:57]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-25 05:23:30]

Patchset 1 (id:??) landed as
https://crrev.com/40f883687274257f05d2f933602318fcc6a5ed7f
Cr-Commit-Position: refs/heads/master@{#340401}

[tfarina, 2015-07-25 17:01:44]

It does not look like related.

Maybe it under covered something that was being hidden in the ChromeOS build by
the analyze step?

[dcheng, 2015-07-25 17:06:19]

The tree went green after the revert landed, so unfortunately, I'd say it's very
much related.

[dcheng, 2015-07-25 17:07:26]

http://build.chromium.org/p/chromium.linux/builders/Linux%20Tests%20%28dbg%29...

vs

http://build.chromium.org/p/chromium.linux/builders/Linux%20Tests%20%28dbg%29...

[tfarina, 2015-07-25 17:17:26]

On 2015/07/25 17:06:19, dcheng wrote:
> The tree went green after the revert landed, so unfortunately, I'd say it's
very
> much related.

Does it mean that DCHECK(context->GetUserData(UserDataKey())); needs user_prefs
to be a shared library to work? Why wouldn't this check work when it is a static
library?

[brettw, 2015-07-25 20:59:17]

Hey Thiago:

If you have two components that each depend on a static library or source set,
that static library or source set will be duplicated in each component. This is
fine for small things if there aren't too many things depending on it, but if
you do certain things like have a singleton, that singleton will now be
duplicated in each component. I suspect that's what's happening to you here.

I would not recommend messing with any component stuff, either adding or
removing them. I bet a lot can be removed, but it's almost impossible to tell
which ones. I did a few of these when doing the GN build and gave up.