PassOwnArrayPtr, PassOwnPtr, PassRefPtr: remove unneeded ASSERT_NOT_REACHED

Remove runtime assertions from places which had been checked already at compile time.

Review URL: https://codereview.chromium.org/25425003

git-svn-id: svn://svn.chromium.org/blink/trunk@158854 bbb929c8-8fbe-4397-9dbb-9b2b20218538