Ctrl-U double-mapped to Format-Underline and View-Source/Visual

```
What steps will reproduce the problem?
1. Hit Ctrl-U

What is the expected output? Underlined text
What do you see instead? Toggle between Source and WYSIWYG

What version of the product are you using? 0.5.1
On what operating system? XUbuntu 14.04




```

Original issue reported on code.google.com by `mheartw...@gmail.com` on 8 Mar 2015 at 6:58
