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=

Review URL: https://codereview.chromium.org/115243009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242587 0039d316-1c4b-4281-b951-d872f2087c98