Some apps may want to check whether they are trusted to install apps on the device, so they can prompt the user to go to settings and mark them as trusted before they do an intensive operation like downloading an apk. Test: cts-tradefed run cts -m CtsExternalSourcesTestCases Bug: 31002700 Change-Id: Icd9d04daa157e6733decba245ec251ce4acd4122