Revert of Returning kApp window handles in GetWebViewIds to make them discoverable (https://codereview.chromium.org/115243009/)

Reason for revert:
This CL breaks some java tests on Windows (http://build.chromium.org/p/chromium.chromedriver/builders/Win7/builds/1580) and Mac (http://build.chromium.org/p/chromium.chromedriver/builders/Mac%2010.6/builds/3207).

The root cause is that "Settings" is of type "app" in chrome 33, while it is of type "background_page" for chrome 31, 32 and TOT for some  reason that is unknown to me.

I'd like to revert this CL first, because I can't find a good fix for it and also found some other problems during looking into the break (I will put up a CL that points out these problems).

Original issue's description:
> Returning kApp window handles in GetWebViewIds to make them discoverable
> 
> Previously this change caused some tests to fail but should be fixed now with  https://chromiumcodereview.appspot.com/113673003/
> 
> BUG=
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=242587

TBR=frankf@chromium.org,chrisgao@chromium.org,bustamante@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=

Review URL: https://codereview.chromium.org/148503004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247363 0039d316-1c4b-4281-b951-d872f2087c98