Remove the FrameStateComplete case from FrameLoader::checkLoadCompleteForThisFrame

BUG=none

Review URL: https://chromiumcodereview.appspot.com/21275002

git-svn-id: svn://svn.chromium.org/blink/trunk@155635 bbb929c8-8fbe-4397-9dbb-9b2b20218538