dart2js: get:hashCode methods to avoid Object.hashCode

pkg/compiler/lib/src/tree/nodes.dart

Index: pkg/compiler/lib/src/tree/nodes.dart
diff --git a/pkg/compiler/lib/src/tree/nodes.dart b/pkg/compiler/lib/src/tree/nodes.dart
index d2e9d965310e3a9b28f2ab85d4e8537f864e442f..1885e0d17865a2dd3bba07e978ed2daa89c387bf 100644
--- a/pkg/compiler/lib/src/tree/nodes.dart
+++ b/pkg/compiler/lib/src/tree/nodes.dart
@@ -295,10 +295,10 @@ Token firstBeginToken(Node first, Node second) {
  * "Token".
  */
 abstract class Node extends NullTreeElementMixin implements Spannable {
-  final int hashCode;
+  final int hashCode = _HASH_COUNTER = (_HASH_COUNTER + 1).toUnsigned(30);
   static int _HASH_COUNTER = 0;
 
-  Node() : hashCode = ++_HASH_COUNTER;
+  Node();
 
   accept(Visitor visitor);