Bug 41443 overview ruler not working
smoke test for 20030812 The overview ruler in the Java editor does not work when starting with a fresh workspace as described in the smoke test scenario.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/JavaEditor.java
ISourceViewer sourceViewer= getSourceViewer();
			if (sourceViewer != null && affectsTextPresentation(new PropertyChangeEvent(event.getSource(), event.getProperty(), event.getOldValue(), event.getNewValue())))
				sourceViewer.invalidateTextPresentation();
		}
	}
	
	/*
	 * @see org.eclipse.ui.texteditor.ITextEditorExtension3#showChangeInformation(boolean)
	 */
	public void showChangeInformation(boolean show) {
		if (show == fIsChangeInformationShown)
			return;
		
		if (fIsChangeInformationShown) {
			uninstallChangeRulerModel();
			showChangeRuler(false); 
		} else {
			ensureChangeInfoCanBeDisplayed(); 
			installChangeRulerModel();
		}
		
		fIsChangeInformationShown= show;
	}
	/**
	 * Installs the differ annotation model with the current quick diff display. 
	 * @since R3.0
	 */
	private void installChangeRulerModel() {
		IChangeRulerColumn column= getChangeColumn();
		if (column != null)