Change List constructors.

samples/dartcombat/grids.dart

Index: samples/dartcombat/grids.dart
diff --git a/samples/dartcombat/grids.dart b/samples/dartcombat/grids.dart
index bf482a3afc19d787b65df84fa1ba60d8293849f3..88b556d9cda41ad2bfefcdb5be9534d247bcd4f2 100644
--- a/samples/dartcombat/grids.dart
+++ b/samples/dartcombat/grids.dart
@@ -19,9 +19,9 @@ class Boat {
 class BoatGrid {
   List<List<Boat>> boatMap;
 
-  BoatGrid() : boatMap = new List(Constants.SIZE) {
+  BoatGrid() : boatMap = new List.fixedLength(Constants.SIZE) {
     for (int i = 0; i < Constants.SIZE; i++) {
-      boatMap[i] = new List(10);
+      boatMap[i] = new List.fixedLength(10);
     }
   }
 
@@ -59,9 +59,9 @@ class GridState {
   List<List<int>> cells;
 
   GridState()
-      : cells = new List(Constants.SIZE) {
+      : cells = new List.fixedLength(Constants.SIZE) {
     for (int i = 0; i < Constants.SIZE; i++) {
-      cells[i] = new List(10);
+      cells[i] = new List.fixedLength(10);
     }
   }