QTabBar shows scroll buttons without need

If scroll buttons are enabled in a QTabBar, they show up without need depending on the text in the tabs. For example, a single tab with the text "25 " (with two spaces at the end) makes them show up, if spaces are added or removed they disappear. (It seems that four characters make them appear, but I've not tested this extensively).

An example application using QTabWidget is attached, the behavior of QTabBar on its own is the same.

The problem occurs on Cocoa and Carbon with Qt 4.8.x. Qt 4.7.5 works correctly. The change that caused this regression issue is:
http://qt.gitorious.org/qt/qt/merge_requests/583

After testing this for a while it looks like the following kind of change is enough to fix this:

static QString computeElidedText(Qt::TextElideMode mode, const QString &text)
{
if (text.length() <= 3)

change this to:

static QString computeElidedText(Qt::TextElideMode mode, const QString &text)
{
if (text.length() <= 4)