The view selector should only deal with view switching, so move the
logic to deal with search (find-as-you-type, cancelling a search,
navigating/activating results) into the SearchTab.
https://bugzilla.gnome.org/show_bug.cgi?id=634948
The view selector is a tabbed interface with a search entry. Starting
a search switches focus to the results' tab, ending a search moves the
focus back to the previously selected tab. Activating a normal tab
while a search is active cancels the search.
https://bugzilla.gnome.org/show_bug.cgi?id=634948
