Use List instead of Link in the type system.

tests/compiler/dart2js/members_test.dart

Index: tests/compiler/dart2js/members_test.dart
diff --git a/tests/compiler/dart2js/members_test.dart b/tests/compiler/dart2js/members_test.dart
index 558be71fd3523bc1b0afd2538c114dd66ad6419c..1a185c9f2893f61b800541b00d7162630075dbb8 100644
--- a/tests/compiler/dart2js/members_test.dart
+++ b/tests/compiler/dart2js/members_test.dart
@@ -253,7 +253,7 @@ void testClassMembers() {
 
     ClassElement B = env.getElement('B');
     InterfaceType B_this = B.thisType;
-    TypeVariableType B_T = B_this.typeArguments.head;
+    TypeVariableType B_T = B_this.typeArguments.first;
     checkMemberCount(B_this, 4 /*inherited*/ + 4 /*non-static declared*/,
                      interfaceMembers: true);
     checkMemberCount(B_this, 4 /*inherited*/ + 5 /*declared*/,
@@ -278,7 +278,7 @@ void testClassMembers() {
 
     ClassElement C = env.getElement('C');
     InterfaceType C_this = C.thisType;
-    TypeVariableType C_S = C_this.typeArguments.head;
+    TypeVariableType C_S = C_this.typeArguments.first;
     checkMemberCount(C_this, 8 /*inherited*/, interfaceMembers: true);
     checkMemberCount(C_this, 8 /*inherited*/, interfaceMembers: false);
     InterfaceType B_S = instantiate(B, [C_S]);
@@ -626,8 +626,8 @@ void testMixinMembers() {
     ClassElement B = env.getElement('B');
     ClassElement C = env.getElement('C');
     InterfaceType C_this = C.thisType;
-    TypeVariableType C_U = C_this.typeArguments.head;
-    TypeVariableType C_V = C_this.typeArguments.tail.head;
+    TypeVariableType C_U = C_this.typeArguments[0];
+    TypeVariableType C_V = C_this.typeArguments[1];
     InterfaceType A_U = instantiate(A, [C_U]);
     InterfaceType B_V = instantiate(B, [C_V]);