(Please change component as needed, not sure where this should go)

Chrome Version: 55.0.2883.75 (Official Build) (64-bit)
OS: Reproduced on Linux, Android. possibly more

What steps will reproduce the problem?
```python
import time
import json
import sys
import os
import threading
import socket

from selenium import webdriver

# Set chromedriver path here if needed
driver = webdriver.Chrome()

driver.set_page_load_timeout(1)
driver.get('https://www.google.com')

driver.set_script_timeout(1)

# Hangs here.
print driver.execute_async_script("while(true) { console.log('hi') }")

driver.quit()
```

What is the expected result?
The browser should timeout on the running script after 1 second.

What happens instead?
No timeout, the browser hangs indefinitely, and no response is made over the JSON wire protocol.

Additional Info:
A simple Wireshark capture shows that Chrome never responds to the execute script request, despite a successful setting of the timeout beforehand. 
A timeout is received if the given javascript does complete without calling the callback, but not if the javascript fails to finish before the timeout.