Bug 278550 [Databinding] ObservablesManager, ObservableTracker and MapSimpleValueObservableMap lead to exception
bundles/org.eclipse.core.databinding.observable/src/org/eclipse/core/databinding/observable/ObservableTracker.java
/**
	 * Threadlocal storage pointing to the current Set of IObservables, or null
	 * if none. Note that this is actually the top of a stack. Whenever a method
	 * changes the current value, it remembers the old value as a local variable
	 * and restores the old value when the method exits.
	 */
	private static ThreadLocal currentChangeListener = new ThreadLocal();
	private static ThreadLocal currentStaleListener = new ThreadLocal();
	private static ThreadLocal currentGetterCalledSet = new ThreadLocal();
	private static ThreadLocal currentObservableCreatedSet = new ThreadLocal();
	/**