Fix DOMWindow::isCurrentlyDisplayedInFrame to return false when detached

Right now, this can return true even if the frame is detached, since it
doesn't check that the frame has a non-null host.

The remaining changes in DOMWindow are to preserve current web visible
behavior, as well as fixing a null pointer dereferences that this exposes
in Performance and ScreenOrientation.

BUG=347331
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/131113003

git-svn-id: svn://svn.chromium.org/blink/trunk@168256 bbb929c8-8fbe-4397-9dbb-9b2b20218538