Replace DeviceDataProvider with the non-templated WifiDataProvider.
Also replace DeviceDataProvider::ListenerInterface with WifiDataProvider::WifiDataUpdateCallback. I would have preferred to do that as a separate change, but removing the templating revealed a nasty circular dependency that involved this nested class, which made forward declarations impossible. So, all in one go then.
I also deleted device_data_provider_unittest.cc as its purpose was to test for threading failures. These data providers no longer start their own threads, see https://codereview.chromium.org/
22866005/
BUG=103713
TBR=jam
Review URL: https://chromiumcodereview.appspot.com/
23181009
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@219279 0039d316-1c4b-4281-b951-d872f2087c98