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
fActionGroups.fillActionBars(actionBars);
        toolBar.add(fHistoryDropDownAction);
        for (int i = 0; i < fToggleCallModeActions.length; i++) {
            toolBar.add(fToggleCallModeActions[i]);
        }
    }
    private KeyListener createKeyListener() {
        KeyListener keyListener = new KeyAdapter() {
                public void keyReleased(KeyEvent event) {
                    handleKeyEvent(event);
                }
            };
        return keyListener;
    }
    /**
     *
     */
    private void makeActions() {
        fRefreshAction = new RefreshAction(this);
        fOpenLocationAction = new OpenLocationAction(getSite());
        fLocationViewer.addOpenListener(new IOpenListener() {
                public void open(OpenEvent event) {
                    fOpenLocationAction.run();
                }
            });
        
        fFocusOnSelectionAction = new FocusOnSelectionAction(this);
        fCopyAction= new CopyCallHierarchyAction(this, fClipboard, fCallHierarchyViewer);
        fSearchScopeActions = new SearchScopeActionGroup(this, fDialogSettings);
        fFiltersActionGroup = new CallHierarchyFiltersActionGroup(this,