Revert of Added event to networkingPrivate extension that portal detection is completed.

Revert of Added event to networkingPrivate extension that portal detection is completed. (https://codereview.chromium.org/225413005/)

Reason for revert:
Fails compile on Chromium Mac.

errors like

../../chrome/browser/extensions/api/networking_private/networking_private_apitest.cc:139:3:error: expected '{' or ','
  bool RunNetworkingSubtest(const std::string& subtest) {

link: http://build.chromium.org/p/chromium.mac/builders/Mac%20Builder/builds/1840/

Original issue's description:
> Added event to networkingPrivate extension that portal detection is completed.
> 
> BUG=354946
> TEST=ExtensionNetworkingPrivateApiTest.*
> R=yoz@chromium.org
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=262736

TBR=yoz@chromium.org,ygorshenin@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=354946

[tapted, 2014-04-09 18:00:09]

Created Revert of Added event to networkingPrivate extension that portal
detection is completed.

[tapted, 2014-04-09 18:00:33]

The CQ bit was unchecked by tapted@chromium.org

[tapted, 2014-04-09 18:01:57]

lost the revert race ;)

unchecked CQ && closing.