separated from bug 1434305 comment #83. Currently findScripts reports JSScripts which has code, it guarantees the script itself and inner scripts are successfully compiled, but it doesn't guarantee the ancestor scripts are successfully compiled, because the ancestor scripts can fail while emitting the code after compiling the inner JSScripts, and the inner JSScripts can live until they get GCed, and findScripts can find them meanwhile. To address this issue, we should somehow invalidate all descendant scripts when the enclosing script fails to compile.