Use union type parts when check if type is subtype.

compiler/java/com/google/dart/compiler/type/InterfaceTypeUnionImplementation.java

Index: compiler/java/com/google/dart/compiler/type/InterfaceTypeUnionImplementation.java
diff --git a/compiler/java/com/google/dart/compiler/type/InterfaceTypeUnion.java b/compiler/java/com/google/dart/compiler/type/InterfaceTypeUnionImplementation.java
similarity index 80%
copy from compiler/java/com/google/dart/compiler/type/InterfaceTypeUnion.java
copy to compiler/java/com/google/dart/compiler/type/InterfaceTypeUnionImplementation.java
index c3eca3b606ca9b66909949ff3670f4ad4321ae7a..b17a4d3a5173614f652cace73df87b04e27e7a53 100644
--- a/compiler/java/com/google/dart/compiler/type/InterfaceTypeUnion.java
+++ b/compiler/java/com/google/dart/compiler/type/InterfaceTypeUnionImplementation.java
@@ -1,4 +1,4 @@
-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
@@ -11,22 +11,22 @@ import com.google.dart.compiler.resolver.ClassElementUnion;
 import java.util.List;
 
 /**
- * Artificial {@link InterfaceType} which is union of several {@link InterfaceType}s.
+ * Implementation of {@link InterfaceTypeUnion}.
  */
-class InterfaceTypeUnion implements InterfaceType {
-  
+class InterfaceTypeUnionImplementation implements InterfaceTypeUnion {
+
   private final List<InterfaceType> types;
   private final ClassElement element;
 
-  public InterfaceTypeUnion(List<InterfaceType> types) {
+  public InterfaceTypeUnionImplementation(List<InterfaceType> types) {
     this.types = types;
     this.element = new ClassElementUnion(this, types);
   }
-  
+
   @Override
   public boolean equals(Object obj) {
-    if (obj instanceof InterfaceTypeUnion) {
-      InterfaceTypeUnion other = (InterfaceTypeUnion) obj;
+    if (obj instanceof InterfaceTypeUnionImplementation) {
+      InterfaceTypeUnionImplementation other = (InterfaceTypeUnionImplementation) obj;
       return getElement().equals(other.getElement());
     }
     return false;
@@ -44,7 +44,7 @@ class InterfaceTypeUnion implements InterfaceType {
   public String toString() {
     return types.toString();
   }
-  
+
   @Override
   public TypeKind getKind() {
     return TypeKind.INTERFACE;
@@ -95,17 +95,21 @@ class InterfaceTypeUnion implements InterfaceType {
     }
     return null;
   }
-  
+
   @Override
   public void registerSubClass(ClassElement subClass) {
   }
-  
+
   @Override
   public void unregisterSubClass(ClassElement subClass) {
   }
-  
+
   @Override
   public Member lookupSubTypeMember(String name) {
     return null;
   }
+
+  public List<InterfaceType> getTypes() {
+    return types;
+  }
 }