4 files changed, 27 insertions, 1 deletions
diff --git a/components/script/dom/documentfragment.rs b/components/script/dom/documentfragment.rs
index 2f0ccecda5c..3eac9df6bac 100644
--- a/components/script/dom/documentfragment.rs
+++ b/components/script/dom/documentfragment.rs
@@ -17,6 +17,7 @@ use dom::eventtarget::{EventTarget, EventTargetTypeId};
 use dom::htmlcollection::HTMLCollection;
 use dom::node::{Node, NodeTypeId, window_from_node};
 use dom::nodelist::NodeList;
+use string_cache::Atom;
 use util::str::DOMString;
 
 // https://dom.spec.whatwg.org/#documentfragment
@@ -58,6 +59,18 @@ impl DocumentFragmentMethods for DocumentFragment {
         HTMLCollection::children(window.r(), NodeCast::from_ref(self))
     }
 
+    // https://dom.spec.whatwg.org/#dom-nonelementparentnode-getelementbyid
+    fn GetElementById(&self, id: DOMString) -> Option<Root<Element>> {
+        let node = NodeCast::from_ref(self);
+        let id = Atom::from_slice(&id);
+        node.traverse_preorder().filter_map(ElementCast::to_root).find(|descendant| {
+            match descendant.get_attribute(&ns!(""), &atom!(id)) {
+                None => false,
+                Some(attr) => *attr.value().as_atom() == id,
+            }
+        })
+    }
+
     // https://dom.spec.whatwg.org/#dom-parentnode-firstelementchild
     fn GetFirstElementChild(&self) -> Option<Root<Element>> {
         NodeCast::from_ref(self).child_elements().next()
diff --git a/components/script/dom/webidls/Document.webidl b/components/script/dom/webidls/Document.webidl
index 203e8d00d1c..fa69f6f95f7 100644
--- a/components/script/dom/webidls/Document.webidl
+++ b/components/script/dom/webidls/Document.webidl
@@ -26,7 +26,6 @@ interface Document : Node {
   HTMLCollection getElementsByTagName(DOMString localName);
   HTMLCollection getElementsByTagNameNS(DOMString? namespace, DOMString localName);
   HTMLCollection getElementsByClassName(DOMString classNames);
-  Element? getElementById(DOMString elementId);
 
   [NewObject, Throws]
   Element createElement(DOMString localName);
@@ -65,6 +64,8 @@ interface Document : Node {
   TreeWalker createTreeWalker(Node root, optional unsigned long whatToShow = 0xFFFFFFFF,
                               optional NodeFilter? filter = null);
 };
+
+Document implements NonElementParentNode;
 Document implements ParentNode;
 
 enum DocumentReadyState { "loading", "interactive", "complete" };
diff --git a/components/script/dom/webidls/DocumentFragment.webidl b/components/script/dom/webidls/DocumentFragment.webidl
index 7dfbcc573df..eb2b7d6696d 100644
--- a/components/script/dom/webidls/DocumentFragment.webidl
+++ b/components/script/dom/webidls/DocumentFragment.webidl
@@ -8,4 +8,5 @@
 interface DocumentFragment : Node {
 };
 
+DocumentFragment implements NonElementParentNode;
 DocumentFragment implements ParentNode;
diff --git a/components/script/dom/webidls/NonElementParentNode.webidl b/components/script/dom/webidls/NonElementParentNode.webidl
new file mode 100644
index 00000000000..b1bd854ab93
--- /dev/null
+++ b/components/script/dom/webidls/NonElementParentNode.webidl
@@ -0,0 +1,11 @@
+/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// https://dom.spec.whatwg.org/#nonelementparentnode
+[NoInterfaceObject,
+ Exposed=Window]
+interface NonElementParentNode {
+  Element? getElementById(DOMString elementId);
+};