Remove debug log message from web_usb_client_impl.cc.

Remove debug log message from web_usb_client_impl.cc.

I accidentally left this debug message in web_usb_client_impl.cc after
debugging connection error issues when working on what became commit
869af1c5170c48b8987b7ce4e2c70c9b37f9beb7.

BUG=None

Committed: https://crrev.com/e426727ce035a30172b8ab2450cc7b330dfac1f1
Cr-Commit-Position: refs/heads/master@{#352387}

[Reilly Grant (use Gerrit), 2015-10-05 18:15:55]

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

[Reilly Grant (use Gerrit), 2015-10-05 18:15:56]

Please take a look.

[Ken Rockot(use gerrit already), 2015-10-05 18:17:18]

lgtm

[Reilly Grant (use Gerrit), 2015-10-05 18:18:13]

The CQ bit was checked by reillyg@chromium.org

[commit-bot: I haz the power, 2015-10-05 18:19:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1373753003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1373753003/1

[commit-bot: I haz the power, 2015-10-05 19:31:54]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-05 19:34:34]

Patchset 1 (id:??) landed as
https://crrev.com/e426727ce035a30172b8ab2450cc7b330dfac1f1
Cr-Commit-Position: refs/heads/master@{#352387}