Add List.first.

sdk/lib/_internal/compiler/implementation/lib/interceptors.dart

Index: sdk/lib/_internal/compiler/implementation/lib/interceptors.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/interceptors.dart b/sdk/lib/_internal/compiler/implementation/lib/interceptors.dart
index ca685dc784e9984b85f518893488d88e93268d73..871ac31e12a3a844d0d8f2f92ca8ade2044b89fd 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/interceptors.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/interceptors.dart
@@ -154,6 +154,13 @@ insertRange$3(receiver, start, length, initialValue) {
   return listInsertRange(receiver, start, length, initialValue);
 }
 
+get$first(receiver) {
+  if (!isJsArray(receiver)) {
+    return UNINTERCEPTED(receiver.first);
+  }
+  return receiver[0];
+}
+
 get$last(receiver) {
   if (!isJsArray(receiver)) {
     return UNINTERCEPTED(receiver.last);