Use List instead of Link in the type system.

sdk/lib/_internal/compiler/implementation/elements/elements.dart

Index: sdk/lib/_internal/compiler/implementation/elements/elements.dart
diff --git a/sdk/lib/_internal/compiler/implementation/elements/elements.dart b/sdk/lib/_internal/compiler/implementation/elements/elements.dart
index 4b367ec125066ea24b3a5b8f6ed8e95b89372cd8..d54aea2d7ca2db1b16727b102401b7b5747b3ff2 100644
--- a/sdk/lib/_internal/compiler/implementation/elements/elements.dart
+++ b/sdk/lib/_internal/compiler/implementation/elements/elements.dart
@@ -1056,7 +1056,7 @@ abstract class TypeDeclarationElement extends Element implements AstElement {
    * available until the type of the element has been computed through
    * [computeType].
    */
-  Link<DartType> get typeVariables;
+  List<DartType> get typeVariables;
 
   bool get isResolved;
 
@@ -1161,7 +1161,7 @@ abstract class ClassElement extends TypeDeclarationElement
 
   void forEachBackendMember(void f(Element member));
 
-  Link<DartType> computeTypeParameters(Compiler compiler);
+  List<DartType> computeTypeParameters(Compiler compiler);
 
   /// Looks up the member [name] in this class.
   Member lookupClassMember(Name name);