Bug 125600 [Field Assist] - popup shell should be resizable with size retained
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ContentProposalAdapter.java
private void addControlListener() {
			targetControlListener = new TargetControlListener();
			control.addListener(SWT.KeyDown, targetControlListener);
			control.addListener(SWT.Traverse, targetControlListener);
		}
		/*
		 * Remove any listeners installed on the control.
		 */
		private void removeControlListener() {
			control.removeListener(SWT.KeyDown, targetControlListener);
			control.removeListener(SWT.Traverse, targetControlListener);
		}
		/*
		 * Answer true if the popup is valid, which means the table has been
		 * created and not disposed.
		 */
		private boolean isValid() {
			return proposalTable != null && !proposalTable.isDisposed();
		}
		/*
		 * Return whether the receiver has focus.
		 */
		private boolean hasFocus() {
			if (!isValid())
				return false;
			return getShell().isFocusControl()
					|| proposalTable.isFocusControl();
		}
		/*
		 * Return the current selected proposal.