Make first and last getters.

runtime/bin/path_impl.dart

Index: runtime/bin/path_impl.dart
diff --git a/runtime/bin/path_impl.dart b/runtime/bin/path_impl.dart
index 2d04e9e83e1ed514e656d408bc1be899b14e8c38..d3467dfacd05c25a36abb30ee307dc6e4ca494e5 100644
--- a/runtime/bin/path_impl.dart
+++ b/runtime/bin/path_impl.dart
@@ -69,7 +69,7 @@ class _Path implements Path {
       for (int i = common; i < pathSegments.length - 1; i++) {
         sb.add('${pathSegments[i]}/');
       }
-      sb.add('${pathSegments.last()}');
+      sb.add('${pathSegments.last}');
       if (hasTrailingSeparator) {
         sb.add('/');
       }
@@ -119,7 +119,7 @@ class _Path implements Path {
         segs[pos] = null;
       }
     }
-    if (segs.last() == '') segs.removeLast();  // Path ends with /.
+    if (segs.last == '') segs.removeLast();  // Path ends with /.
     // No remaining segments can be ., .., or empty.
     return !segs.some((s) => s == '' || s == '.' || s == '..');
   }
@@ -146,7 +146,7 @@ class _Path implements Path {
             } else {
               newSegs.add('..');
             }
-          } else if (newSegs.last() == '..') {
+          } else if (newSegs.last == '..') {
             newSegs.add('..');
           } else {
             newSegs.removeLast();