In diverse scenarios the method getPreferredVisualRepresentation is called too
often. As this call can be very expensive for charts with big data or 3D charts,
the superfluous calls must be avoided.

1) Activate an existing chart leads to calls of getPreferredVisualRepresentation:
-in writer 2 times what is superfluous
-in calc and impress zero times as it should be
2) Deactivating an unmodified chart leads to calls of
getPreferredVisualRepresentation:
-one time for writer, calc and impress but there is no need to change the
representation, or?
3) Deactivating a modified chart leads to calls of getPreferredVisualRepresentation:
- 2 times in writer, calc and impress - there should be only one call instead
4) Editing a chart in impress leads to an immediate call of
getPreferredVisualRepresentation - seems to be superfluous also
5) when creating a default chart getPreferredVisualRepresentation is called very
often in writer over 10 times. In calc and impress its called only once which
might be ok, not sure - maybe this calls can also be avoided.