Adding isNotEmpty property to collection and string.

sdk/lib/_internal/compiler/implementation/mirrors/util.dart

Index: sdk/lib/_internal/compiler/implementation/mirrors/util.dart
diff --git a/sdk/lib/_internal/compiler/implementation/mirrors/util.dart b/sdk/lib/_internal/compiler/implementation/mirrors/util.dart
index 7760da1e633cfb90074da26e862d0937c339ff3a..72b05b9fcd181d763a5e8cbb3933dc9e6b4b94dc 100644
--- a/sdk/lib/_internal/compiler/implementation/mirrors/util.dart
+++ b/sdk/lib/_internal/compiler/implementation/mirrors/util.dart
@@ -58,6 +58,7 @@ abstract class AbstractMap<K,V> implements Map<K,V> {
   }
 
   bool get isEmpty => length == 0;
+  bool get isNotEmpty => !isEmpty;
   V putIfAbsent(K key, V ifAbsent()) {
     if (!containsKey(key)) {
       V value = this[key];