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
return getShell();
	}
	/**
	 * Returns the title image label.
	 * 
	 * @return the title image label
	 */
	protected Label getTitleImageLabel() {
		return titleImageLabel;
	}
	/**
	 * Display the given error message. The currently displayed message is saved
	 * and will be redisplayed when the error message is set to
	 * <code>null</code>.
	 * 
	 * @param newErrorMessage
	 *            the newErrorMessage to display or <code>null</code>
	 */
	public void setErrorMessage(String newErrorMessage) {
		
		if (errorMessage == null ? newErrorMessage == null : errorMessage
				.equals(newErrorMessage))
			return;
		errorMessage = newErrorMessage;
		
		if (errorMessage == null) {
			if (showingError) {
				
				showingError = false;
			}