Add support for using DOM Distiller in incognito.

Add support for using DOM Distiller in incognito.

Currently the DOM Distiller does not work in incognito, since the source
for the chrome-distiller:// scheme has not been registered.

This CL moves the functionality for registering the scheme to a generic place
and it is now used by both ProfileImpl and by OffTheRecordProfile during
profile creation.

It also makes both the normal profile and the incognito profile use the same
instance of the DomDistillerService.

BUG=380036
Committed: https://crrev.com/6e3ab0a5c3ca6fcb76a736107e08dbbbf1e2637a
Cr-Commit-Position: refs/heads/master@{#296974}

[nyquist, 2014-09-25 21:05:31]

nyquist@chromium.org changed reviewers:
+ cjhopman@chromium.org

[nyquist, 2014-09-25 21:05:32]

cjhopman: PTAL

[nyquist, 2014-09-25 22:30:16]

nyquist@chromium.org changed reviewers:
+ erg@chromium.org

[nyquist, 2014-09-25 22:30:17]

erg: PTAL chrome/browser/profiles

[cjhopman, 2014-09-25 22:35:48]

lgtm

[Elliot Glaysher, 2014-09-26 17:27:27]

lgtm

[nyquist, 2014-09-26 17:28:23]

The CQ bit was checked by nyquist@chromium.org

[commit-bot: I haz the power, 2014-09-26 17:29:27]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/608653002/1

[commit-bot: I haz the power, 2014-09-26 17:54:35]

Committed patchset #1 (id:1) as b2c2dca570dc64f39716e03678e4f43c9da64bfc

[commit-bot: I haz the power, 2014-09-26 17:55:25]

Patchset 1 (id:??) landed as
https://crrev.com/6e3ab0a5c3ca6fcb76a736107e08dbbbf1e2637a
Cr-Commit-Position: refs/heads/master@{#296974}