Convert the autofill interactive browser test to a normal browser_test. I added testing methods to fake input events that don't depend on the OS and being at the front.

BUG=121574
Review URL: https://chromiumcodereview.appspot.com/10368010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@135432 0039d316-1c4b-4281-b951-d872f2087c98