[TMF] add public getters for fields used in TimeGraphControl.drawState

[TMF] add public getters for fields used in TimeGraphControl.drawState

TimeGraphControl.drawState() is protected, and therefore can be overridden.
Unfortunately, this method uses two private fields: fEventColorMap and
fTimeGraphProvider. Therefore, in order to be able to override this method,
these two fields must have accessible getters.

Change-Id: Ia82d422f33b8a8c205b761104340b4d293fae33a
Signed-off-by: Xavier Raynaud <xavier.raynaud@kalray.eu>
Reviewed-on: https://git.eclipse.org/r/20424
Tested-by: Hudson CI
Reviewed-by: Patrick Tasse <patrick.tasse@gmail.com>
IP-Clean: Patrick Tasse <patrick.tasse@gmail.com>