Fix a type warning for SVGElement.tag.

client/html/dartium/html_dartium.dart

Index: client/html/dartium/html_dartium.dart
diff --git a/client/html/dartium/html_dartium.dart b/client/html/dartium/html_dartium.dart
index 4421359392bdce9bd5942dae568307309ebf82a7..5a1a980991f249bc61c13ecf98d29716ef5fd62f 100644
--- a/client/html/dartium/html_dartium.dart
+++ b/client/html/dartium/html_dartium.dart
@@ -36366,8 +36366,11 @@ class _DocumentFragmentFactoryProvider {
 }
 
 class _SVGElementFactoryProvider {
-  factory SVGElement.tag(String tag) =>
-    _document._createElementNS("http://www.w3.org/2000/svg", tag);
+  factory SVGElement.tag(String tag) {
+    final Element temp =
+      _document._createElementNS("http://www.w3.org/2000/svg", tag);
+    return temp;
+  }
 
   factory SVGElement.svg(String svg) {
     Element parentTag;