Fix dart2js Uint32x4List in checked mode

sdk/lib/typed_data/dart2js/typed_data_dart2js.dart

Index: sdk/lib/typed_data/dart2js/typed_data_dart2js.dart
diff --git a/sdk/lib/typed_data/dart2js/typed_data_dart2js.dart b/sdk/lib/typed_data/dart2js/typed_data_dart2js.dart
index f8a1c6131fc516bc109b1e280acf225a050268c1..57c371eb2b65ced49116310fbdab714d688f5293 100644
--- a/sdk/lib/typed_data/dart2js/typed_data_dart2js.dart
+++ b/sdk/lib/typed_data/dart2js/typed_data_dart2js.dart
@@ -870,10 +870,10 @@ class Uint32x4List
 
   Uint32x4 operator[](int index) {
     _checkIndex(index, length);
-    double _x = _storage[(index*4)+0];
-    double _y = _storage[(index*4)+1];
-    double _z = _storage[(index*4)+2];
-    double _w = _storage[(index*4)+3];
+    int _x = _storage[(index*4)+0];
+    int _y = _storage[(index*4)+1];
+    int _z = _storage[(index*4)+2];
+    int _w = _storage[(index*4)+3];
     return new Uint32x4(_x, _y, _z, _w);
   }