Flame graph shifts when source view is opened

Profile: https://share.firefox.dev/3rKKxGY

Steps to reproduce:

1. Double click a function in the flame graph.

Expected results: The source view should open and the flame graph's contents should stay where they are.

Actual results: When the source view opens, the flame graph's contents are moved upwards by the source view height. The function you just double-clicked is no longer under the mouse, and in fact it might be pushed completely offscreen.

┆Issue is synchronized with this Jira Task