In Nightly, right-click inspect the dragonfish's photophore. Notice how the page jumps down, hiding the dragon fish when the devvtools pop up. Dragonfish's head should remain visible.
This is working to a pretty good standard. Takes about 100 lines of javascript to account for viewport-based sizing having weird interaction with scroll/window-resize.
In Nightly, right-click inspect the dragonfish's photophore. Notice how the page jumps down, hiding the dragon fish when the devvtools pop up. Dragonfish's head should remain visible.