Browser extension & native integration conflicting on Bitbucket Server

Created by: tsenart

• Sourcegraph version: 3.6.0-rc.1

Steps to reproduce:

1. Point your Sourcegraph extension to https://k8s.sgdev.org
2. Go to https://bitbucket.sgdev.org/projects/SOUR/repos/vegeta/browse/encode.go?at=master#88
3. Hover over the NewCSVEncoder symbol and move the pointer horizontally over the symbol until two tooltips pop-up.

Expected behavior:

Only one tooltip shows up.

Actual behavior:

Two tooltips are shown, although with different content (note how the one in the back has the type of the argument as io.Writer and the one in the front only Writer).