Could you provide a list of code needing that update? This would allow a faster and more complete change.
A subclass of AbstractTimeGraphView that doesn't use getTimeGraphCombo() should work out of the box, whether it uses columns or not.
In most cases calls to getTimeGraphCombo() can get replaced with getTimeGraphViewer().
Calls to setSelection(entry) on the combo should be replaced with setSelection(entry, true) on the time graph viewer.
If the user called getTree() on the combo, the tree returned by the time graph viewer only has column headers and no tree items. For example CallStackView was adding an IDoubleClickListener on the tree. This had to be replaced by a mouseDoubleClick() MouseListener on the time graph control, with the selection fetched from the viewer instead of from the DoubleClickEvent. That was the hardest update required in Trace Compass.