Bug 36981 call hierarchy: Search scope should be persisted
Search scope should be persisted when the platform shuts down or when the view is closed and reopened.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/callhierarchy/CallHierarchyViewPart.java
this.fCalleeRoot = calleeRoot;
    }
    private MethodWrapper getCalleeRoot() {
        if (fCalleeRoot == null) {
            fCalleeRoot = (MethodWrapper) CallHierarchy.getDefault().getCalleeRoot(fShownMethod);
        }
        return fCalleeRoot;
    }
    private void setCallerRoot(MethodWrapper callerRoot) {
        this.fCallerRoot = callerRoot;
    }
    private MethodWrapper getCallerRoot() {
        if (fCallerRoot == null) {
            fCallerRoot = (MethodWrapper) CallHierarchy.getDefault().getCallerRoot(fShownMethod);
        }
        return fCallerRoot;
    }
    /**
     * Adds the entry if new. Inserted at the beginning of the history entries list.
     */
    private void addHistoryEntry(IJavaElement entry) {
        if (fMethodHistory.contains(entry)) {
            fMethodHistory.remove(entry);
        }
        fMethodHistory.add(0, entry);
        fHistoryDropDownAction.setEnabled(!fMethodHistory.isEmpty());
    }
    /**
     * @param parent
     */