Fix dead code hints in summary code.

pkg/analyzer/lib/src/summary/summarize_elements.dart

Index: pkg/analyzer/lib/src/summary/summarize_elements.dart
diff --git a/pkg/analyzer/lib/src/summary/summarize_elements.dart b/pkg/analyzer/lib/src/summary/summarize_elements.dart
index 59b05d0c3d9795ad8fcf9cdf7945986ec56c5989..a0777d439b8d51c06b1dd8ef26aec8bf62d2631b 100644
--- a/pkg/analyzer/lib/src/summary/summarize_elements.dart
+++ b/pkg/analyzer/lib/src/summary/summarize_elements.dart
@@ -540,12 +540,9 @@ class _LibrarySerializer {
   UnlinkedTypeRefBuilder serializeTypeRef(DartType type, Element context) {
     UnlinkedTypeRefBuilder b = new UnlinkedTypeRefBuilder(ctx);
     if (type is TypeParameterType) {
-      Element enclosingElement = type.element.enclosingElement;
       b.paramReference = findTypeParameterIndex(type, context);
     } else {
       Element element = type.element;
-      CompilationUnitElement dependentCompilationUnit =
-          element.getAncestor((Element e) => e is CompilationUnitElement);
       LibraryElement dependentLibrary = element.library;
       if (dependentLibrary == null) {
         assert(type.isDynamic);