Test merge editor: compare with base should maybe open at the line where the merge editor was

[andreamah]

Testing #158819

Not sure if this is expected behavior, but comparing with base opens at the top of the file regardless of where in the merge editor I was. I think it'd be more helpful to open to where I was in the merge editor, since I'd maybe be more interested in what that particular part of the base had?

[hediet]

@andreamah can you verify? :)

[andreamah]

I notice that, if I don't click into the editor that I'm asking for the base view from, it still starts from the beginning. See below:

Otherwise, it works great!