Bug 1358448 - Add radio back to a radio group after moving out of a form. r=smaug

The container of a radio group is the form, if it belongs to a form, or the
document object otherwise.
When moving a radio out of a form, we should add it back to a radio group.
Similary, before moving the radio to a form, we should remove it from the
original radio group.

MozReview-Commit-ID: 22WsEhz2SXH

dom/html/HTMLInputElement.cpp

@@ -1550,6 +1550,27 @@ HTMLInputElement::AfterSetAttr(int32_t aNameSpaceID, nsIAtom* aName,
                                                          aValue, aNotify);
 }
 
+void
+HTMLInputElement::BeforeSetForm(bool aBindToTree)
+{
+  // No need to remove from radio group if we are just binding to tree.
+  if (mType == NS_FORM_INPUT_RADIO && !aBindToTree) {
+    WillRemoveFromRadioGroup();
+  }
+}
+
+void
+HTMLInputElement::AfterClearForm(bool aUnbindOrDelete)
+{
+  MOZ_ASSERT(!mForm);
+
+  // Do not add back to radio group if we are releasing or unbinding from tree.
+  if (mType == NS_FORM_INPUT_RADIO && !aUnbindOrDelete) {
+    AddedToRadioGroup();
+    UpdateValueMissingValidityStateForRadio(false);
+  }
+}
+
 // nsIDOMHTMLInputElement
 
 NS_IMETHODIMP