Uppercase element.tagName for HTML elements only

Fixes #3146

1 files changed, 8 insertions, 8 deletions

diff --git a/src/components/script/dom/element.rs b/src/components/script/dom/element.rs
index 37889c861f1..203b0099116 100644
--- a/src/components/script/dom/element.rs
+++ b/src/components/script/dom/element.rs
@@ -491,14 +491,14 @@ impl<'a> ElementMethods for JSRef<'a, Element> {
 
     // http://dom.spec.whatwg.org/#dom-element-tagname
     fn TagName(&self) -> DOMString {
-        match self.prefix {
-            None => {
-                self.local_name.as_slice().to_ascii_upper()
-            }
-            Some(ref prefix_str) => {
-                let s = format!("{}:{}", prefix_str, self.local_name);
-                s.as_slice().to_ascii_upper()
-            }
+        let qualified_name = match self.prefix {
+            Some(ref prefix) => format!("{}:{}", prefix, self.local_name).into_maybe_owned(),
+            None => self.local_name.as_slice().into_maybe_owned()
+        };
+        if self.html_element_in_html_document() {
+            qualified_name.as_slice().to_ascii_upper()
+        } else {
+            qualified_name.into_string()
         }
     }