Chrome version: 67.0.3396.87 Channel: stable
OS Version: 4.15.0-29-generic #31-Ubuntu SMP x86_64 x86_64 x86_64 GNU/Linux
Flash Version: not installed

Steps to reproduce the problem:

1. Install the Opera extension "Install Chrome Extensions" https://addons.opera.com/en/extensions/details/install-chrome-extensions/
2. Install some Chrome and Opera extensions.
3. Launch Opera-Chromium browser with --single-process
4. After a few minutes of browsing on multiple tabs, click an extension button.

What is the expected behavior?
Extension popup will open.

What went wrong?
Opera-Chromium crashes

Crashed report ID in about://crashes: Not available in Opera-Chromium

How much crashed? Whole browser

Did this work before? No

no probs if remove --single-process switch

Reported to Google here:
https://bugs.chromium.org/p/chromium/issues/detail?id=871431