Bug 37464 call hierarchy: Should not use working copies
The call hierarchy should not use working copies of compilation units since these may go away (e.g. when an editor is closed).
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/callhierarchy/CallHierarchyViewPart.java
return fViewAdapter; 
    }
    private CallHierarchyViewSiteAdapter getViewSiteAdapter() {
        if (fViewSiteAdapter == null) {
            fViewSiteAdapter= new CallHierarchyViewSiteAdapter(this.getViewSite());
        }
        return fViewSiteAdapter;
    }
    private void showOrHideCallDetailsView() {
        if (fShowCallDetails) {
            fHierarchyLocationSplitter.setMaximizedControl(null);
        } else {
            fHierarchyLocationSplitter.setMaximizedControl(fCallHierarchyViewer.getControl());
        }
    }
    private void updateLocationsView(MethodWrapper methodWrapper) {
        if (methodWrapper != null && methodWrapper.getMethodCall().hasCallLocations()) {
            fLocationViewer.setInput(methodWrapper.getMethodCall().getCallLocations());
        } else {
            fLocationViewer.setInput(""); 
        }
    }
    private void updateHistoryEntries() {
        for (int i = fMethodHistory.size() - 1; i >= 0; i--) {
            IMethod method = (IMethod) fMethodHistory.get(i);
            if (!method.exists()) {
                fMethodHistory.remove(i);
            }
        }
        fHistoryDropDownAction.setEnabled(!fMethodHistory.isEmpty());