Remove DownloadItem::Is*() in favor of DI::GetState()

Rationale here is that we don't need two different ways of getting the
same state information.

BUG=241141
TEST=browser_tests/unit_tests/content_unittests w/ *Download*:*SavePage*

Review URL: https://chromiumcodereview.appspot.com/16994004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@206604 0039d316-1c4b-4281-b951-d872f2087c98
11 files changed