Slow page render on GitHub with browser extension enabled

Created by: eatonphil

• Chrome browser integration

Steps to reproduce:

1. Visit this Standard ML file while the browser integration is enabled and try to scroll down https://github.com/eatonphil/ponyo/blob/master/examples/performance-testing.sml
2. It takes seconds to render the content
3. Visit the same file without the browser integration enabled and it renders about as quickly as you scrol

Expected behavior:

If the language is not supported (by looking at file extensions?) don't render it through Sourcegraph.

Actual behavior:

A non-supported language is re-rendered through Sourcegraph and causes unnecessarily slow page renders.