[route]

handle_error checked the result's subtype instead of exceptionDetails, so:

• throw "smth", throw { code: 1 } or a promise rejected with a non-Error value were returned as the result of evaluate, execute, evaluate_async and evaluate_on instead of raising
• returning (not throwing) an Error object crashed with NoMethodError, because JavaScriptError was built from missing exceptionDetails

Now any exceptionDetails raises JavaScriptError (or ScriptTimeoutError for the async timeout), and a returned Error is converted like any other object. For a thrown primitive the message includes the value, e.g. Uncaught smth instead of Uncaught; thrown Errors keep the same class_name, message and stack_trace.

The existing evaluate(%(throw "smth")) spec only passed because the return wrapper made it a syntax error; the new specs throw for real and fail without the fix.

Cuprite's custom JS errors all extend Error, so its behavior doesn't change: session_spec.rb and driver_spec.rb pass against this branch.