Extract //device/usb mocks so that they can be shared.

Extract //device/usb mocks so that they can be shared.

A number of browser and unit tests use mocks of the UsbService,
UsbDevice and UsbDeviceHandle classes. This change de-duplicates them.

Committed: https://crrev.com/cf9be26f35fa706d770ae59dd6d185aed84edc17
Cr-Commit-Position: refs/heads/master@{#329856}

[Reilly Grant (use Gerrit), 2015-05-14 00:00:33]

reillyg@chromium.org changed reviewers:
+ rockot@chromium.org

[Reilly Grant (use Gerrit), 2015-05-14 00:00:33]

Please review this pretty boring change.

[Reilly Grant (use Gerrit), 2015-05-14 00:45:06]

reillyg@chromium.org changed reviewers:
+ phajdan.jr@chromium.org

[Reilly Grant (use Gerrit), 2015-05-14 00:45:06]

Adding Paweł for //chrome/test/BUILD.gn.

[Paweł Hajdan Jr., 2015-05-14 10:06:40]

LGTM

[Ken Rockot(use gerrit already), 2015-05-14 14:52:59]

lgtm

[Reilly Grant (use Gerrit), 2015-05-14 15:02:08]

The CQ bit was checked by reillyg@chromium.org

[commit-bot: I haz the power, 2015-05-14 15:03:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1144493003/60001

[commit-bot: I haz the power, 2015-05-14 16:06:23]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-05-14 16:07:19]

Patchset 4 (id:??) landed as
https://crrev.com/cf9be26f35fa706d770ae59dd6d185aed84edc17
Cr-Commit-Position: refs/heads/master@{#329856}