UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36

Steps to reproduce the problem:
1. Create and install an extension with the following code in the background page:

chrome.webRequest.onHeadersReceived.addListener(
  details =>
  {
    console.log("onHeadersReceived", details);
  }, {urls: ["https://regex101.com/*", "https://reddit.com/*"]},
  ["blocking", "responseHeaders"]
);

2. Inspect the extension's background page. 
3. Browse to https://regex101.com/ in a new tab.
4. Browse to https://www.reddit.com/ in a new tab.
5. Look through the "onHeadersReceived ..." logs in the console for the extension's background page.

What is the expected behavior?
The first response for both reddit and regex101 should have the type of "main_frame". Both should have a tabId > -1.

What went wrong?
The response for regex101 is reported as having the type "xmlhttprequest" and a tabId of -1.

The response for reddit worked OK.

Did this work before? N/A 

Does this work in other browsers? N/A

Chrome version: 63.0.3239.132  Channel: n/a
OS Version: 
Flash Version: 

This is relevant for extensions such as Adblock Plus and uBlock.