Bug 27114 something leaks StyleRanges and Lines
180K of StyleReanges and 47K of Lines after: -open editor -close editor seems like StyleRange objects are never freed
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/JavaEditor.java
*/
	private void showLineNumberRuler() {
		IVerticalRuler v= getVerticalRuler();
		if (v instanceof CompositeRuler) {
			CompositeRuler c= (CompositeRuler) v;
			c.addDecorator(1, createLineNumberRulerColumn());
		}
	}
	
	/**
	 * Hides the line number ruler column.
	 */
	private void hideLineNumberRuler() {
		IVerticalRuler v= getVerticalRuler();
		if (v instanceof CompositeRuler) {
			CompositeRuler c= (CompositeRuler) v;
			c.removeDecorator(1);
		}
	}
	
	/**
	 * Return whether the line number ruler column should be 
	 * visible according to the preference store settings.
	 * @return <code>true</code> if the line numbers should be visible
	 */
	private boolean isLineNumberRulerVisible() {
		IPreferenceStore store= getPreferenceStore();
		return store.getBoolean(LINE_NUMBER_RULER);
	}