Viewport height not calculated correctly inside Weave Cloud

[fbarl]

This is how the bottom part of Table View looks like in standalone Scope UI:

And this is what we get for the same version of Scope UI running inside of Weave Cloud:

The scrollbar overflow indicates there is something wrong with how the viewport height is calculated. In fact, since we get it from window.height, the margins might be correct only when Scope covers the whole screen. That's not the case with Weave Cloud because of the top navigation bar and it might also not be the case generally when showing Scope in an iFrame.