Bug 249915 [Dialogs] TitleAreaDialog does not short circuit if message is null
M20080911-1700 When profiling use of a custom WizardDialog on Linux/GTK, a lot of time was spent in WizardPage.setMessage(...). It turns out that this was because we were setting a message of null after each keypress, and the page's description (DialogPage.getDescription()) was also null. In this case the short-circuit in TitleAreaDialog.setMessage(String, int) fails to notice that the message has not changed, and does a layout every time. For our dialog this takes about 40ms each time, which is noticeable when compounded with other work.
bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/TitleAreaDialog.java
String shownMessage = (newImage == null) ? message : " " + message;   
		messageImage = newImage;
		if (!showingError) {
			
			updateMessage(shownMessage);
			messageImageLabel.setImage(messageImage);
			setImageLabelVisible(messageImage != null);
			layoutForNewMessage();
		}
	}
	/**
	 * Update the contents of the messageLabel.
	 * 
	 * @param newMessage
	 *            the message to use
	 */
	private void updateMessage(String newMessage) {
		messageLabel.setText(newMessage);
	}
	/**
	 * Sets the title to be shown in the title area of this dialog.
	 * 
	 * @param newTitle
	 *            the title show
	 */
	public void setTitle(String newTitle) {
		if (titleLabel == null)
			return;
		String title = newTitle;
		if (title == null)