Checks that setScriptSource fails when editing the top-most stack frame, but that function also has an activation further down the stack
First pause at (before live edit):
function testExpression(a, b) {
  #debugger;
  if (!a && !b) {

Second pause at (before live edit):
function testExpression(a, b) {
  #debugger;
  if (!a && !b) {

Debugger.setScriptSource result:
{
    status : BlockedByActiveFunction
}
Evaluation result:
{
    description : 8
    type : number
    value : 8
}