Bug 1409183: Don't consider anonymous checkboxes as part of the document radio group. r=smaug

Summary: In this case the radiobox is in a SVG <use> subtree.

Reviewers: smaug

Bug #: 1409183

Differential Revision: https://phabricator.services.mozilla.com/D741

MozReview-Commit-ID: Abkg7ahST5t

dom/html/HTMLInputElement.cpp

@@ -3213,6 +3213,10 @@ HTMLInputElement::GetRadioGroupContainer() const
     return mForm;
   }
 
+  if (IsInAnonymousSubtree()) {
+    return nullptr;
+  }
+
   //XXXsmaug It isn't clear how this should work in Shadow DOM.
   return static_cast<nsDocument*>(GetUncomposedDoc());
 }
@@ -6680,7 +6684,7 @@ HTMLInputElement::AddedToRadioGroup()
 {
   // If the element is neither in a form nor a document, there is no group so we
   // should just stop here.
-  if (!mForm && !IsInUncomposedDoc()) {
+  if (!mForm && (!IsInUncomposedDoc() || IsInAnonymousSubtree())) {
     return;
   }