Implement getClassicLeastUpperBound() in IncrementalClassHierarchy.

pkg/kernel/test/class_hierarchy_test.dart

Index: pkg/kernel/test/class_hierarchy_test.dart
diff --git a/pkg/kernel/test/class_hierarchy_test.dart b/pkg/kernel/test/class_hierarchy_test.dart
index 56b4eb64b27e2b4296b42f2fa7b1b7bc5c279293..a67db37993b0c8264df55caeff89aa0461183773 100644
--- a/pkg/kernel/test/class_hierarchy_test.dart
+++ b/pkg/kernel/test/class_hierarchy_test.dart
@@ -48,21 +48,6 @@ class IncrementalClassHierarchyTest extends _ClassHierarchyTest {
   }
 
   @failingTest
-  void test_getClassicLeastUpperBound_expansive() {
-    super.test_getClassicLeastUpperBound_expansive();
-  }
-
-  @failingTest
-  void test_getClassicLeastUpperBound_generic() {
-    super.test_getClassicLeastUpperBound_generic();
-  }
-
-  @failingTest
-  void test_getClassicLeastUpperBound_nonGeneric() {
-    super.test_getClassicLeastUpperBound_nonGeneric();
-  }
-
-  @failingTest
   void test_getDispatchTarget() {
     super.test_getDispatchTarget();
   }