Bug 32254 [Viewers] AbstractTreeViewer uses HashSet to remember expansion state
I20030216 The custom hash table should be used instead. Otherwise expansion state may be lost due to a different equals implementation of the element and the IElementComparer.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/StructuredViewer.java
for (Iterator i = filters.iterator(); i.hasNext();) {
				Object o = i.next();
				if (o == filter) {
					i.remove();
					refresh();
					if (filters.size() == 0)
						filters = null;
					return;
				}
			}
		}
	}
	/**
	 * Discards this viewer's filters and triggers refiltering and resorting of
	 * the elements.
	 */
	public void resetFilters() {
		if (filters != null) {
			filters = null;
			refresh();
		}
	}
	/**
	 * Ensures that the given element is visible, scrolling the viewer if
	 * necessary. The selection is unchanged.
	 * 
	 * @param element
	 *            the element to reveal