Fix failing test introduced by commit 2688d444.

Change-Id: I29cbafc3a513bb00a6f999047d1ada5e0da6201f
diff --git a/dev/core/test/com/google/gwt/dev/jjs/JavaAstConstructor.java b/dev/core/test/com/google/gwt/dev/jjs/JavaAstConstructor.java
index 6eb0415..ca55f21 100644
--- a/dev/core/test/com/google/gwt/dev/jjs/JavaAstConstructor.java
+++ b/dev/core/test/com/google/gwt/dev/jjs/JavaAstConstructor.java
@@ -192,9 +192,10 @@
           "package java.lang;",
           "import java.io.Serializable;",
           "import com.google.gwt.core.client.JavaScriptObject;",
+          "import jsinterop.annotations.JsIgnore;",
           "import jsinterop.annotations.JsType;",
           "@JsType public abstract class Enum<E extends Enum<E>> implements Serializable {",
-          "  public static native <T extends Enum<T>> T valueOf(Class<T> enumType,",
+          "  @JsIgnore public static native <T extends Enum<T>> T valueOf(Class<T> enumType,",
           "      String name) /*-{ return enumType + name; }-*/;",
           "  public static native <T extends Enum<T>> T valueOf(JavaScriptObject enumType,",
           "      String name) /*-{ return enumType + name; }-*/;",