Adding supported checks for HttpRequestProgressEvent.

sdk/lib/html/dartium/html_dartium.dart

Index: sdk/lib/html/dartium/html_dartium.dart
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index b7fca7421e3f5abdac67561e47f6f5d8464d7e66..9337574645c0efbf8a8a3137defc3fc7e09afc56 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -13698,9 +13698,15 @@ class HttpRequestException extends NativeFieldWrapperClass1 {
 
 @DocsEditable
 @DomName('XMLHttpRequestProgressEvent')
+@SupportedBrowser(SupportedBrowser.CHROME)
+@SupportedBrowser(SupportedBrowser.SAFARI)
+@Experimental()
 class HttpRequestProgressEvent extends ProgressEvent {
   HttpRequestProgressEvent.internal() : super.internal();
 
+  /// Checks if this type is supported on the current platform.
+  static bool get supported => true;
+
   @DomName('XMLHttpRequestProgressEvent.position')
   @DocsEditable
   int get position native "XMLHttpRequestProgressEvent_position_Getter";