Add LibraryElementForLink.isDartCore.

pkg/analyzer/test/src/summary/linker_test.dart

Index: pkg/analyzer/test/src/summary/linker_test.dart
diff --git a/pkg/analyzer/test/src/summary/linker_test.dart b/pkg/analyzer/test/src/summary/linker_test.dart
index e5f0dfabb287a049466d3c4338fe1b7bcb410b36..ef33f950ea6c1669ba092fcb3f82db9a4ce566b1 100644
--- a/pkg/analyzer/test/src/summary/linker_test.dart
+++ b/pkg/analyzer/test/src/summary/linker_test.dart
@@ -454,6 +454,20 @@ class D extends C {
         'int');
   }
 
+  void test_leastUpperBound_functionAndClass() {
+    createLinker('''
+class C {}
+void f() {}
+var x = {
+  'C': C,
+  'f': f
+};
+''');
+    LibraryElementForLink library = linker.getLibrary(linkerInputs.testDartUri);
+    library.libraryCycleForLink.ensureLinked();
+    // No assertions--just make sure it doesn't crash.
+  }
+
   void test_libraryCycle_ignoresDependenciesOutsideBuildUnit() {
     createLinker('import "dart:async";');
     LibraryCycleForLink libraryCycle = testLibrary.libraryCycleForLink;