Reuse RuntimeTypesNeedBuilderImpl and _RuntimeTypesNeed for kernel based elements

pkg/compiler/lib/src/elements/types.dart

Index: pkg/compiler/lib/src/elements/types.dart
diff --git a/pkg/compiler/lib/src/elements/types.dart b/pkg/compiler/lib/src/elements/types.dart
index 6e84728e19da76f8102ac9f05b0203ba390667b4..4ddcef3227b853d01ed5b7a3318201b42f491327 100644
--- a/pkg/compiler/lib/src/elements/types.dart
+++ b/pkg/compiler/lib/src/elements/types.dart
@@ -736,4 +736,14 @@ abstract class DartTypes {
   /// Returns `true` if [t] might be a subtype of [s] for some values of
   /// type variables in [s] and [t].
   bool isPotentialSubtype(DartType t, DartType s);
+
+  /// Returns [type] as an instance of [cls] or `null` if [type] is not a
+  /// subtype of [cls].
+  ///
+  /// For instance `asInstanceOf(List<String>, Iterable) = Iterable<String>`.
+  InterfaceType asInstanceOf(InterfaceType type, ClassEntity cls);
+
+  /// Returns the supertype of [cls], i.e. the type in the `extends` clause of
+  /// [cls].
+  InterfaceType getSupertype(ClassEntity cls);
 }