3 files changed, 16 insertions, 10 deletions
diff --git a/components/script/dom/htmliframeelement.rs b/components/script/dom/htmliframeelement.rs
index a4d1958445b..552730a2bb3 100644
--- a/components/script/dom/htmliframeelement.rs
+++ b/components/script/dom/htmliframeelement.rs
@@ -437,8 +437,12 @@ impl HTMLIFrameElementMethods for HTMLIFrameElement {
     // https://developer.mozilla.org/en-US/docs/Web/API/Using_the_Browser_API
     // https://developer.mozilla.org/en-US/docs/Web/HTML/Element/iframe#attr-mozbrowser
     fn Mozbrowser(&self) -> bool {
-        let element = self.upcast::<Element>();
-        element.has_attribute(&atom!("mozbrowser"))
+        if window_from_node(self).is_mozbrowser() {
+            let element = self.upcast::<Element>();
+            element.has_attribute(&atom!("mozbrowser"))
+        } else {
+            false
+        }
     }
 
     // https://developer.mozilla.org/en-US/docs/Web/HTML/Element/iframe#attr-mozbrowser
diff --git a/components/script/dom/webidls/BrowserElement.webidl b/components/script/dom/webidls/BrowserElement.webidl
index 9bb34b90a95..2767fa15071 100644
--- a/components/script/dom/webidls/BrowserElement.webidl
+++ b/components/script/dom/webidls/BrowserElement.webidl
@@ -146,16 +146,16 @@ interface BrowserElementPrivileged {
   //                    unsigned long count,
   //                    unsigned long modifiers);
 
-  [Throws]
+  [Func="Window::global_is_mozbrowser", Throws]
   void goBack();
 
-  [Throws]
+  [Func="Window::global_is_mozbrowser", Throws]
   void goForward();
 
-  [Throws]
+  [Func="Window::global_is_mozbrowser", Throws]
   void reload(optional boolean hardReload = false);
 
-  [Throws]
+  [Func="Window::global_is_mozbrowser", Throws]
   void stop();
 
   //[Throws,
diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index 0f21139c324..4862cb83c9e 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -1459,15 +1459,17 @@ impl Window {
         })
     }
 
+    /// Returns whether this window is mozbrowser.
+    pub fn is_mozbrowser(&self) -> bool {
+        mozbrowser_enabled() && self.parent_info().is_none()
+    }
+
     /// Returns whether mozbrowser is enabled and `obj` has been created
     /// in a top-level `Window` global.
     #[allow(unsafe_code)]
     pub unsafe fn global_is_mozbrowser(_: *mut JSContext, obj: HandleObject) -> bool {
-        if !mozbrowser_enabled() {
-            return false;
-        }
         match global_root_from_object(obj.get()).r() {
-            GlobalRef::Window(window) => window.parent_info().is_none(),
+            GlobalRef::Window(window) => window.is_mozbrowser(),
             _ => false,
         }
     }