Make isEmpty a getter.

lib/compiler/implementation/util/link.dart

Index: lib/compiler/implementation/util/link.dart
diff --git a/lib/compiler/implementation/util/link.dart b/lib/compiler/implementation/util/link.dart
index 1029363bbdca4d9b1874b0dd95f2246d26cb75c9..eab6b96096cd50f7108d25bef253e537fabfd7df 100644
--- a/lib/compiler/implementation/util/link.dart
+++ b/lib/compiler/implementation/util/link.dart
@@ -39,12 +39,12 @@ class Link<T> implements Iterable<T> {
 
   List toList() => new List<T>(0);
 
-  bool isEmpty() => true;
+  bool get isEmpty => true;
 
   Link<T> reverse() => this;
 
   Link<T> reversePrependAll(Link<T> from) {
-    if (from.isEmpty()) return this;
+    if (from.isEmpty) return this;
     return this.prepend(from.head).reversePrependAll(from.tail);
   }
 
@@ -52,7 +52,7 @@ class Link<T> implements Iterable<T> {
 
   bool operator ==(other) {
     if (other is !Link<T>) return false;
-    return other.isEmpty();
+    return other.isEmpty;
   }
 
   String toString() => "[]";