Revert of Set use_rndis_forwarder in platform backend.

Revert of Set use_rndis_forwarder in platform backend. (patchset #2 id:20001 of https://codereview.chromium.org/860913003/)

Reason for revert:
Speculative revert for BUG=452080
Original issue's description:
> Remove the android SetRndisForwarder() call from browser_backend and set it
> directly in the platform_backend
> 
> When the needs_browser_restart_after_each_page flag is set to true in the page
> test, we initialize the browser_backend twice and call SetRndisForwarder()
> twice. Instead, we can make this call for the platform once.
> 
> Additionally, I added a simple unittest for the case when this flag is set.
> 
> BUG=450331
> 
> Committed: https://crrev.com/d26579b485b0cb323af99487c524ac8ff751e2ef
> Cr-Commit-Position: refs/heads/master@{#312882}

TBR=ariblue@google.com
BUG=450331

[nednguyen, 2015-03-09 21:07:35]

Created Revert of Set use_rndis_forwarder in platform backend.

[nednguyen, 2015-03-09 21:08:10]

The CQ bit was checked by nednguyen@google.com

[commit-bot: I haz the power, 2015-03-09 21:08:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/994583004/1

[commit-bot: I haz the power, 2015-03-09 21:15:00]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-03-09 21:15:01]

Try jobs failed on following builders:
  ios_dbg_simulator_ninja on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios_dbg_simulator...)
  ios_rel_device_ninja on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios_rel_device_ni...)