When reviewing it can be useful to jump back and forth between specific

files or parts of the patch. Right now this requires scrolling all the

way to the top of the page and clicking the desired file, or remembering

where it is (which can be difficult in a large diff).
To improve this experience, the file list will dock itself as a

"banner widget" into the unified review banner. As a "banner widget",

the file list will work as a drop down showing the current file and

expanding to jump to other files.