selecting a really long file name from the share links search popup causes the window to resize unnecessarily

[Mike McCracken]

If you search for a file that has a really long path , like one in a shared folder, then select it, it will resize the main window to fit the whole filename in the widget.
This can be way too big.

this occurred on darwin.

here's an example path:

u'/Users/mmccrack/Ubuntu One/Shared With Me/U1_design_share (Lisette, fe76df32-6a95-4a6d-ab74-e4512c50b8e9)/Web/web1_apps/Music_Store/design_drafts/homepage/no_overlays_02.png'

note that this also causes the UI to hang, but I've filed that as a separate bug, bug #1061949