Bug 19014 Empty CU after reorg
F2 - enable single click and show in members in packages view - open TestCase.java in editor - give focus to packages view - change it on disk - copy a method in TestCase using DnD - activate the TestCase.java editor - answer question with no - activate revert from context menu observe: CU is empty
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/CompilationUnitDocumentProvider.java
return null;
			}
		};
		
		/**
		 * Internal structure for mapping positions to some value. 
		 * The reason for this specific structure is that positions can
		 * change over time. Thus a lookup is based on value and not
		 * on hash value.
		 */
		protected static class ReverseMap {
			
			static class Entry {
				Position fPosition;
				Object fValue;
			};
			
			private List fList= new ArrayList(2);
			private int fAnchor= 0;
			
			public ReverseMap() {
			}
			
			public Object get(Position position) {
				
				Entry entry;
				
				
				int length= fList.size();
				for (int i= fAnchor; i < length; i++) {