Could AbstractTab#isVisible() be backported to 1.3-branch?

[Edvin Syse]

Hi,

I see that AbstractTab has gotten an isVisible() method in the 
1.4-branch, would it be possible to backport this to 1.3? I can't 
upgrade to 1.4 yet, and need this functionality :)

Sincerely,
Edvin Syse