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
data.top = new FormAttachment(messageImageLabel, 0, SWT.TOP);
		data.left = new FormAttachment(0, 0);
		data.bottom = new FormAttachment(messageImageLabel, 0, SWT.BOTTOM);
		data.right = new FormAttachment(messageImageLabel, 0);
		leftFillerLabel.setLayoutData(data);
	}
	/**
	 * The <code>TitleAreaDialog</code> implementation of this
	 * <code>Window</code> methods returns an initial size which is at least
	 * some reasonable minimum.
	 * 
	 * @return the initial size of the dialog
	 */
	protected Point getInitialSize() {
		Point shellSize = super.getInitialSize();
		return new Point(Math.max(
				convertHorizontalDLUsToPixels(MIN_DIALOG_WIDTH), shellSize.x),
				Math.max(convertVerticalDLUsToPixels(MIN_DIALOG_HEIGHT),
						shellSize.y));
	}
	/**
	 * Retained for backward compatibility.
	 * 
	 * Returns the title area composite. There is no composite in this
	 * implementation so the shell is returned.
	 * 
	 * @return Composite
	 * @deprecated
	 */
	protected Composite getTitleArea() {