From 5f12940329ba496da5730863cae94cd8c0b145da Mon Sep 17 00:00:00 2001
From: "Matt A. Tobin" <email@mattatobin.com>
Date: Fri, 17 Apr 2020 06:34:38 -0400
Subject: Bug 1396584 - Remove support for multiple ShadowRoots

Tag #1375
---
 dom/base/Element.cpp | 22 +++++-----------------
 1 file changed, 5 insertions(+), 17 deletions(-)

(limited to 'dom/base/Element.cpp')

diff --git a/dom/base/Element.cpp b/dom/base/Element.cpp
index a2b78092a..5bbfbee9b 100644
--- a/dom/base/Element.cpp
+++ b/dom/base/Element.cpp
@@ -1095,6 +1095,11 @@ Element::RemoveFromIdTable()
 already_AddRefed<ShadowRoot>
 Element::CreateShadowRoot(ErrorResult& aError)
 {
+  if (GetShadowRoot()) {
+    aError.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
+    return nullptr;
+  }
+
   nsAutoScriptBlocker scriptBlocker;
 
   RefPtr<mozilla::dom::NodeInfo> nodeInfo;
@@ -1131,24 +1136,7 @@ Element::CreateShadowRoot(ErrorResult& aError)
 
   shadowRoot->SetIsComposedDocParticipant(IsInComposedDoc());
 
-  // Replace the old ShadowRoot with the new one and let the old
-  // ShadowRoot know about the younger ShadowRoot because the old
-  // ShadowRoot is projected into the younger ShadowRoot's shadow
-  // insertion point (if it exists).
-  ShadowRoot* olderShadow = GetShadowRoot();
   SetShadowRoot(shadowRoot);
-  if (olderShadow) {
-    olderShadow->SetYoungerShadow(shadowRoot);
-
-    // Unbind children of older shadow root because they
-    // are no longer in the composed tree.
-    for (nsIContent* child = olderShadow->GetFirstChild(); child;
-         child = child->GetNextSibling()) {
-      child->UnbindFromTree(true, false);
-    }
-
-    olderShadow->SetIsComposedDocParticipant(false);
-  }
 
   // xblBinding takes ownership of docInfo.
   RefPtr<nsXBLBinding> xblBinding = new nsXBLBinding(shadowRoot, protoBinding);
-- 
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