Revert of Include USB printers in printer list as "provisional" devices.

Revert of Include USB printers in printer list as "provisional" devices. (patchset #5 id:80001 of https://codereview.chromium.org/1153173002/)

Reason for revert:
Looks like this broke at least one test on the official builders (http://crbug.com/493584)

Original issue's description:
> Include USB printers in printer list as "provisional" devices.
>
> This patch starts including a list of connected printers supported by
> printerProvider apps in the normal list of extension printers returned
> to the print preview WebUI. These printers are given "provisional" IDs
> because the devices are not yet known to the apps themselves.
>
> BUG=468955
>
> Committed: https://crrev.com/6c3c36136b4567f2225550f15e27d2720e1930d8
> Cr-Commit-Position: refs/heads/master@{#331886}

TBR=vitalybuka@chromium.org,tbarzic@chromium.org,rockot@chromium.org,reillyg@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=468955
Committed: https://crrev.com/faf208b1a9e95b9f10c74246df9449dcc56fef75
Cr-Commit-Position: refs/heads/master@{#332104}

[Nico, 2015-05-30 02:33:38]

Created Revert of Include USB printers in printer list as "provisional" devices.

[commit-bot: I haz the power, 2015-05-30 02:33:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1163743002/1

[commit-bot: I haz the power, 2015-05-30 02:35:24]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-30 02:36:00]

Patchset 1 (id:??) landed as
https://crrev.com/faf208b1a9e95b9f10c74246df9449dcc56fef75
Cr-Commit-Position: refs/heads/master@{#332104}