Implement subtype for type variables.

sdk/lib/_internal/compiler/implementation/resolution/members.dart

Index: sdk/lib/_internal/compiler/implementation/resolution/members.dart
diff --git a/sdk/lib/_internal/compiler/implementation/resolution/members.dart b/sdk/lib/_internal/compiler/implementation/resolution/members.dart
index 8bb3b30a579632e5d9babbf395dafc6f3cc3e2d1..df090e16ea7e43edc8d912f169268fb968ecb9c4 100644
--- a/sdk/lib/_internal/compiler/implementation/resolution/members.dart
+++ b/sdk/lib/_internal/compiler/implementation/resolution/members.dart
@@ -2785,13 +2785,13 @@ class TypeDefinitionVisitor extends CommonResolverVisitor<DartType> {
           warning(node, MessageKind.CYCLIC_TYPE_VARIABLE,
                   {'typeVariableName': variableElement.name});
         } else if (boundType != null) {
-          variableElement.bound = boundType;
+          variableElement.upperBound = boundType;
         } else {
           // TODO(johnniwinther): Should be an erroneous type.
-          variableElement.bound = compiler.objectClass.computeType(compiler);
+          variableElement.upperBound = compiler.objectClass.computeType(compiler);
         }
       } else {
-        variableElement.bound = compiler.objectClass.computeType(compiler);
+        variableElement.upperBound = compiler.objectClass.computeType(compiler);
       }
       nodeLink = nodeLink.tail;
       typeLink = typeLink.tail;