Clicking on file tab should change focus to that flle's buffer

[mandolyte]

To reproduce:

1. open fresh on a folder
2. in file nav click on one or more files
3. move pointer to file tabs and click on one of them
4. do a ctrl+f to do a search

Result: it will not work because the file nav area still has focus.

Desired change: when I click on file tab, that tab should also gain the focus.

(I use both ChromeOS Linux and Ubuntu; the default, built-in terminals in each)