Simulation charts panel in Designer contains two scroll bars - this is confusing; user is not sure which one he should use.

steps to reproduce:
1. open a process in a Designer
2. run a simulation
3. resize the browser
4. take a look at simulation charts - there are two scroll bars

The issue exists since 6.0.0 (shortly mentioned in bug 1007879), still present in 6.2.0.GA

Please see the attached screenshot.