Uri: use List.unmodifiable

sdk/lib/core/uri.dart

Index: sdk/lib/core/uri.dart
diff --git a/sdk/lib/core/uri.dart b/sdk/lib/core/uri.dart
index 3abd352c1ae8e120a6934fe312c064132de29af1..d459a895e04e7bd88a5ceebe660e6cc50e464636 100644
--- a/sdk/lib/core/uri.dart
+++ b/sdk/lib/core/uri.dart
@@ -1009,26 +1009,27 @@ class Uri {
   }
 
   /**
-   * Returns the URI path split into its segments. Each of the
-   * segments in the returned list have been decoded. If the path is
-   * empty the empty list will be returned. A leading slash `/` does
-   * not affect the segments returned.
+   * Returns the URI path split into its segments. Each of the segments in the
+   * returned list have been decoded. If the path is empty the empty list will
+   * be returned. A leading slash `/` does not affect the segments returned.
    *
    * The returned list is unmodifiable and will throw [UnsupportedError] on any
    * calls that would mutate it.
    */
   List<String> get pathSegments {
-    if (_pathSegments == null) {
-      var pathToSplit = !path.isEmpty && path.codeUnitAt(0) == _SLASH
-                        ? path.substring(1)
-                        : path;
-      _pathSegments = new UnmodifiableListView(
-        pathToSplit == "" ? const<String>[]
-                          : pathToSplit.split("/")
-                                       .map(Uri.decodeComponent)
-                                       .toList(growable: false));
-    }
-    return _pathSegments;
+    var result = _pathSegments;
+    if (result != null) return result;
+
+    var pathToSplit = path;
+    if (pathToSplit.isNotEmpty && pathToSplit.codeUnitAt(0) == _SLASH) {
+      pathToSplit = pathToSplit.substring(1);
+    }
+    result = (pathToSplit == "")
+        ? const<String>[]
+        : new List<String>.unmodifiable(
+              pathToSplit.split("/").map(Uri.decodeComponent));
+    _pathSegments = result;
+    return result;
   }
 
   /**