Fix issues with foreignobject sanitizing

tools/dom/src/NodeValidatorBuilder.dart

Index: tools/dom/src/NodeValidatorBuilder.dart
diff --git a/tools/dom/src/NodeValidatorBuilder.dart b/tools/dom/src/NodeValidatorBuilder.dart
index 7789c1b017df9cce1f314b7472a1b0140ca14b0d..7ebeb36dd1deb3155d531f19be3b2161c10ffd8f 100644
--- a/tools/dom/src/NodeValidatorBuilder.dart
+++ b/tools/dom/src/NodeValidatorBuilder.dart
@@ -455,8 +455,9 @@ class _SvgNodeValidator implements NodeValidator {
     }
     // Firefox 37 has issues with creating foreign elements inside a
     // foreignobject tag as SvgElement. We don't want foreignobject contents
-    // anyway, so just remove the whole tree outright.
-    if (element is svg.ForeignObjectElement) {
+    // anyway, so just remove the whole tree outright. And we can't rely
+    // on IE recognizing the SvgForeignObject type, so go by tagName. Bug 23144
+    if (element is svg.SvgElement && element.tagName == 'foreignObject') {
       return false;
     }
     if (element is svg.SvgElement) {