Right now it's possible to invoke the REP escape sequence with a maximum of tens of millions of iterations. In practice, there is never any need to do this. Calling it more frequently than the number of cells in the terminal hardly makes any sense. By placing a limit on it, we can prevent users from exhausting resources in inside the terminal emulator. As support for this escape sequence is not present in any of the stable branches, there is no need to MFC. Reported by: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=11255