Gerrit "All Side by Side" does not open diff in new tabs

Short version:

Each Gerrit review has a button Open Allthat opens each diff in new tabs.

This situation suddenly changed a week ago: now it opens a new window for each file. I could not understand why, although I was looking for this problem.

Do you know what this change can explain, and how can I return to my previous behavior?

Steps to reproduce the problem

• Go to https://android-review.googlesource.com/#/c/82097/ with Firefox
• Press button Open All
• Please note that it opens a lot of new windows, not new tabs.

More practical details:

• Gerrit setting has not changed
• firefox (FF 27). Tool > Options > Tabs > "Open in a new tab rather than a new windows" . ( , firefox ).
• Internet Explorer 9
• Chrome Opera, ( . ).
• Windows