Shift-Selecting by keyboard is really really slooooowwwwwwwww. Really.

It seems like the diff viewer is blocking the keyboard thread when a file selection takes place.

Steps to reproduce

0. Make sure you have plenty changed files
1. Click any file in the file view
2. Press and hold the shift key
3. Hit the down key repeatedly in a fast fashion to select more files

Expected: the file view to keep up with how fast you extend the selection

Actual: the file view lags heavily