Bug 54900 [rulers] Java Editor does not show ruler on external Java files
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/CompilationUnitDocumentProvider.java
info.fElement= element;
			fFakeCUInfoMap.put(element, info);
		}
		info.fCount++;
	}
	
	/*
	 * @see org.eclipse.ui.editors.text.TextFileDocumentProvider#disconnect(java.lang.Object)
	 * @since 3.2
	 */
	public void disconnect(Object element) {
		CompilationUnitInfo info= (CompilationUnitInfo)fFakeCUInfoMap.get(element);
		if (info != null)  {
			if (info.fCount == 1) {
				fFakeCUInfoMap.remove(element);
				
				try {
					info.fCopy.discardWorkingCopy();
				} catch (JavaModelException ex) {
					handleCoreException(ex, ex.getMessage());				}
			} else
				info.fCount--;
		}
		super.disconnect(element);
	}
	
	/**
	 * Creates and returns a new sub-progress monitor for the
	 * given parent monitor.
	 *