Bug 73083 [Encoding] Need to verify encodings and indicate unavailable ones
When the encodings are set up we need to ensure that they are in the list of valid encodings available from the VM. Those that are not should be indicated as such and not be selectable in the UI.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/ide/dialogs/AbstractEncodingFieldEditor.java
public void setPreferenceStore(IPreferenceStore store) {
		super.setPreferenceStore(store);
		defaultEnc = store.getDefaultString(getPreferenceName());
		updateDefaultEncoding();
	}
	private void updateDefaultEncoding() {
		defaultEncodingButton.setText(defaultButtonText()); 
	}
	private Composite getContainer() {
		return container;
	}
	private Group createEncodingGroup(Composite parent, int numColumns) {
		Font font = parent.getFont();
		Group group = new Group(parent, SWT.NONE);
		GridData data = new GridData(GridData.FILL_HORIZONTAL);
		group.setLayoutData(data);
		GridLayout layout = new GridLayout();
		layout.numColumns = 2;
		group.setLayout(layout);
		group.setText(IDEWorkbenchMessages.getString("WorkbenchPreference.encoding")); 
		group.setFont(font);
		SelectionAdapter buttonListener = new SelectionAdapter() {
			public void widgetSelected(SelectionEvent e) {
				updateEncodingState(defaultEncodingButton.getSelection());
				updateValidState();
			}
		};
		defaultEncodingButton = new Button(group, SWT.RADIO);
		defaultEnc = findDefaultEncoding();
		defaultEncodingButton.setText(defaultButtonText());