829: Mainline

Suppose that you tell the GUI builder that the subclass of the ApplicationModel class is to be the ValueHolderDemonstration.

Further suppose that you tell the GUI builder that each of the three widgets is to use a value model obtained from the application model's commonValue instance variable.

Then, the GUI builder will perform the following work for you:

• Define the ValueHolderDemonstration class with a commonValue instance variable.
• Define commonValue, the getter for the commonValue variable.