Tests how let/const declarations interact with command line api.
first 'let a = 1;' result: wasThrown = false
second 'let a = 1;' result: wasThrown = true
exception message: Uncaught SyntaxError: Identifier 'a' has already been declared
{"result":{"type":"number","value":42,"description":"42"}}
function $() { [native code] }
function $$() { [native code] }
function $x() { [native code] }
function dir() { [native code] }
function dirxml() { [native code] }
function keys() { [native code] }
function values() { [native code] }
function profile() { [native code] }
function profileEnd() { [native code] }
function monitorEvents() { [native code] }
function unmonitorEvents() { [native code] }
function inspect() { [native code] }
function copy() { [native code] }
function clear() { [native code] }
function getEventListeners() { [native code] }
function debug() { [native code] }
function undebug() { [native code] }
function monitor() { [native code] }
function unmonitor() { [native code] }
function table() { [native code] }