Reuse RuntimeTypesNeedBuilderImpl and _RuntimeTypesNeed for kernel based elements

pkg/compiler/lib/src/common_elements.dart

Index: pkg/compiler/lib/src/common_elements.dart
diff --git a/pkg/compiler/lib/src/common_elements.dart b/pkg/compiler/lib/src/common_elements.dart
index e113ed2d908b37c0f38595b9b7f5d2a3076358cd..18557548b33e03285e38762a37c8cb52a0a0805b 100644
--- a/pkg/compiler/lib/src/common_elements.dart
+++ b/pkg/compiler/lib/src/common_elements.dart
@@ -1183,7 +1183,7 @@ abstract class ElementEnvironment {
   void forEachClassMember(
       ClassEntity cls, void f(ClassEntity declarer, MemberEntity member));
 
-  /// Returns the declared superclass of [cls].
+  /// Returns the superclass of [cls].
   ///
   /// Unnamed mixin applications are included, for instance for these classes
   ///
@@ -1218,6 +1218,9 @@ abstract class ElementEnvironment {
   /// where the type arguments are the type variables of [cls].
   InterfaceType getThisType(ClassEntity cls);
 
+  /// Returns `true` if [cls] is generic.
+  bool isGenericClass(ClassEntity cls);
+
   /// The upper bound on the [typeVariable]. If not explicitly declared, this is
   /// `Object`.
   DartType getTypeVariableBound(TypeVariableEntity typeVariable);