Fonts in chrome are larger in 102-based alphas for Mac

Here's a side-by-side comparison of 11.5.2 and 12.0a3 for MacOS:

Note how the text in the chrome is all larger, which has the domino effect of:

1. Making the chrome itself taller
2. Decreasing the available canvas area for content
3. Triggering letterboxing unexpectedly
4. Thereby causing the whole browser to open at a smaller default size than usual on MacBooks: 12-0-a3-default-window-size-macbook

That last point could arguably be spun off into a separate issue to improve the responsiveness of the layout on netbooks too.