Fix includes in //components/keyed_service/content

Fix includes in //components/keyed_service/content

Remove unnecessary includes for forward-declared classes in both
refcounted_browser_context_keyed_service_factory.h and
browser_context_keyed_service_factory.h.

Fix other header files broken by this cleanup by addding the
missing include.

BUG=419366
TBR=jochen@chromium.org

Committed: https://crrev.com/997d364ad30fe99c15c8246e2c638e9e55d7e8ad
Cr-Commit-Position: refs/heads/master@{#300250}

[sdefresne, 2014-10-17 12:27:14]

sdefresne@chromium.org changed reviewers:
+ jochen@chromium.org, phajdan.jr@chromium.org

[sdefresne, 2014-10-17 12:27:14]

sdefresne@chromium.org changed required reviewers:
+ phajdan.jr@chromium.org

[sdefresne, 2014-10-17 12:27:14]

phajdan.jr: please take a look at this cleanup CL.

jochen: adding you as OWNERS of //chrome/browser for the refactored files, but I
think this can be TBR-ed

[Paweł Hajdan Jr., 2014-10-17 17:23:01]

LGTM

[sdefresne, 2014-10-20 12:01:48]

The CQ bit was checked by sdefresne@chromium.org

[commit-bot: I haz the power, 2014-10-20 12:02:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/662803002/20001

[commit-bot: I haz the power, 2014-10-20 12:22:17]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2014-10-20 12:23:00]

Patchset 2 (id:??) landed as
https://crrev.com/997d364ad30fe99c15c8246e2c638e9e55d7e8ad
Cr-Commit-Position: refs/heads/master@{#300250}