Converting XHR from onLoad to onReadyStateChange

sdk/lib/html/dart2js/html_dart2js.dart

Index: sdk/lib/html/dart2js/html_dart2js.dart
diff --git a/sdk/lib/html/dart2js/html_dart2js.dart b/sdk/lib/html/dart2js/html_dart2js.dart
index e33d421417b5c54dbd7df861804c9c92101fb578..b398f6ba57bdbcb6af1c704838815e2227912517 100644
--- a/sdk/lib/html/dart2js/html_dart2js.dart
+++ b/sdk/lib/html/dart2js/html_dart2js.dart
@@ -12793,12 +12793,14 @@ class HttpRequest extends EventTarget native "*XMLHttpRequest" {
       xhr.onProgress.listen(onProgress);
     }
 
-    xhr.onLoad.listen((e) {
-      if (xhr.status >= 200 && xhr.status < 300 ||
-          xhr.status == 304 ) {
-        completer.complete(xhr);
-      } else {
-        completer.completeError(e);
+    xhr.onReadyStateChange.listen((e) {
+      if (xhr.readyState == HttpRequest.DONE) {
+        if (xhr.status >= 200 && xhr.status < 300 ||
+            xhr.status == 304 ) {
+          completer.complete(xhr);
+        } else {
+          completer.completeError(e);
+        }
       }
     });