Does what it says, looks like the built-in one.

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To MrGlasspoole:

It is easy to target this extension by the ID:

.webextension-page-action[id="_e1ed7a80-7c11-4f7e-968b-79b551a0067f_-page-action"]

Not sure why you need a go button though when the built-in one is right next to it...