Bug 117071 MembersOrderPreferenceCache leaking a propertyChangeListener
20051109 org.eclipse.jdt.ui.PreferenceConstants#initializeDefaultValues adds a listener to JDT UI preference store but this is not deleted before shutdown.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/JavaPlugin.java
* extension point.
	 * 
	 * @return the registry of contributed <code>IJavaFoldingStructureProvider</code>
	 * @since 3.0
	 */
	public synchronized JavaFoldingStructureProviderRegistry getFoldingStructureProviderRegistry() {
		if (fFoldingStructureProviderRegistry == null)
			fFoldingStructureProviderRegistry= new JavaFoldingStructureProviderRegistry();
		return fFoldingStructureProviderRegistry;
	}
	/**
	 * Returns the Java content assist history.
	 * 
	 * @return the Java content assist history
	 * @since 3.2
	 */
	public ContentAssistHistory getContentAssistHistory() {
		if (fContentAssistHistory == null) {
			try {
				fContentAssistHistory= ContentAssistHistory.load(getPluginPreferences(), PreferenceConstants.CODEASSIST_LRU_HISTORY);
			} catch (CoreException x) {
				log(x);
			}
			if (fContentAssistHistory == null)
				fContentAssistHistory= new ContentAssistHistory();
		}
		return fContentAssistHistory;
	}
}