AAPT2: Cleanup Visitors for XML and Values

Test: make aapt2_tests
Change-Id: Ib61f64c155a380115610edeaf2d65e60258a2426
diff --git a/tools/aapt2/link/ReferenceLinker.cpp b/tools/aapt2/link/ReferenceLinker.cpp
index 71e828b..ad7d8b6 100644
--- a/tools/aapt2/link/ReferenceLinker.cpp
+++ b/tools/aapt2/link/ReferenceLinker.cpp
@@ -42,9 +42,9 @@
 // to the reference object.
 //
 // NOTE: All of the entries in the ResourceTable must be assigned IDs.
-class ReferenceLinkerVisitor : public ValueVisitor {
+class ReferenceLinkerVisitor : public DescendingValueVisitor {
  public:
-  using ValueVisitor::Visit;
+  using DescendingValueVisitor::Visit;
 
   ReferenceLinkerVisitor(const CallSite& callsite, IAaptContext* context, SymbolTable* symbols,
                          StringPool* string_pool, xml::IPackageDeclStack* decl)