Cache important USB string descriptors all at once.

Cache important USB string descriptors all at once.

On platforms without udev support we must open a libusb device handle
in order to read string descriptors from the device. Rapidly opening
and closing the handle could cause problems with the platform's USB
stack so this patch caches the manufacturer, product and serial number
strings all at once. It also prevents a leak of the device handle by
explicitly closing it.

BUG=346953
Committed: https://crrev.com/838d2a5ce4b9fe2ece0d7202c5ea2dfe173aeb89
Cr-Commit-Position: refs/heads/master@{#300116}

[Reilly Grant (use Gerrit), 2014-10-16 21:47:07]

Patchset #1 (id:1) has been deleted

[Reilly Grant (use Gerrit), 2014-10-16 21:47:47]

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

[Reilly Grant (use Gerrit), 2014-10-16 21:48:29]

Please take a look. This fixes the USB device picker on Windows. The issue was
mostly that the handle wasn't always being closed by the previous logic but
caching everything in one go can't hurt.

[rpaquay, 2014-10-17 15:38:04]

lgtm

[Reilly Grant (use Gerrit), 2014-10-17 15:43:08]

The CQ bit was checked by reillyg@chromium.org

[commit-bot: I haz the power, 2014-10-17 15:43:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/659943003/40001

[commit-bot: I haz the power, 2014-10-17 16:41:23]

Committed patchset #2 (id:40001)

[commit-bot: I haz the power, 2014-10-17 16:42:03]

Patchset 2 (id:??) landed as
https://crrev.com/838d2a5ce4b9fe2ece0d7202c5ea2dfe173aeb89
Cr-Commit-Position: refs/heads/master@{#300116}