Description of problem:
After adding a workflow pattern, the step cannot be taken back by clicking Undo. Undo is not even enabled when this is the first action after opening the process, so it seems adding WPs is simply not recorded in the action history.

Version-Release number of selected component (if applicable):
6.2.0.ER3

How reproducible:
-

Steps to Reproduce:
1. Open any process, drag any pattern from 'Workflow Patterns' section in 'Object Library' on the Canvas.
2. Click Undo.

Actual results:
Nothing happens (if Undo is enabled).

Expected results:
Undo must be enabled, the added workflow pattern must be removed.

Additional info: