diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
index 12df916dac1a..6f58a4c21d0b 100644
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -4371,6 +4371,7 @@ nsresult GetEventAndTarget(nsIDocument* aDoc, nsISupports* aTarget,
                            const nsAString& aEventName,
                            CanBubble aCanBubble,
                            Cancelable aCancelable,
+                           Composed aComposed,
                            Trusted aTrusted,
                            Event** aEvent,
                            EventTarget** aTargetOut)
@@ -4385,7 +4386,7 @@ nsresult GetEventAndTarget(nsIDocument* aDoc, nsISupports* aTarget,
     return err.StealNSResult();
   }
 
-  event->InitEvent(aEventName, aCanBubble, aCancelable);
+  event->InitEvent(aEventName, aCanBubble, aCancelable, aComposed);
   event->SetTrusted(aTrusted == Trusted::eYes);
 
   event->SetTarget(target);
@@ -4401,10 +4402,11 @@ nsContentUtils::DispatchTrustedEvent(nsIDocument* aDoc, nsISupports* aTarget,
                                      const nsAString& aEventName,
                                      CanBubble aCanBubble,
                                      Cancelable aCancelable,
+                                     Composed aComposed,
                                      bool* aDefaultAction)
 {
   return DispatchEvent(aDoc, aTarget, aEventName, aCanBubble, aCancelable,
-                       Trusted::eYes, aDefaultAction);
+                       aComposed, Trusted::eYes, aDefaultAction);
 }
 
 // static
@@ -4416,7 +4418,7 @@ nsContentUtils::DispatchUntrustedEvent(nsIDocument* aDoc, nsISupports* aTarget,
                                        bool* aDefaultAction)
 {
   return DispatchEvent(aDoc, aTarget, aEventName, aCanBubble, aCancelable,
-                       Trusted::eNo, aDefaultAction);
+                       Composed::eDefault, Trusted::eNo, aDefaultAction);
 }
 
 // static
@@ -4425,6 +4427,7 @@ nsContentUtils::DispatchEvent(nsIDocument* aDoc, nsISupports* aTarget,
                               const nsAString& aEventName,
                               CanBubble aCanBubble,
                               Cancelable aCancelable,
+                              Composed aComposed,
                               Trusted aTrusted,
                               bool* aDefaultAction,
                               ChromeOnlyDispatch aOnlyChromeDispatch)
@@ -4432,7 +4435,8 @@ nsContentUtils::DispatchEvent(nsIDocument* aDoc, nsISupports* aTarget,
   RefPtr<Event> event;
   nsCOMPtr<EventTarget> target;
   nsresult rv = GetEventAndTarget(aDoc, aTarget, aEventName, aCanBubble,
-                                  aCancelable, aTrusted, getter_AddRefs(event),
+                                  aCancelable, aComposed, aTrusted,
+                                  getter_AddRefs(event),
                                   getter_AddRefs(target));
   NS_ENSURE_SUCCESS(rv, rv);
   event->WidgetEventPtr()->mFlags.mOnlyChromeDispatch =
@@ -4496,7 +4500,8 @@ nsContentUtils::DispatchChromeEvent(nsIDocument *aDoc,
   RefPtr<Event> event;
   nsCOMPtr<EventTarget> target;
   nsresult rv = GetEventAndTarget(aDoc, aTarget, aEventName, aCanBubble,
-                                  aCancelable, Trusted::eYes,
+                                  aCancelable, Composed::eDefault,
+                                  Trusted::eYes,
                                   getter_AddRefs(event),
                                   getter_AddRefs(target));
   NS_ENSURE_SUCCESS(rv, rv);
@@ -4543,7 +4548,8 @@ nsContentUtils::DispatchEventOnlyToChrome(nsIDocument* aDoc,
                                           bool* aDefaultAction)
 {
   return DispatchEvent(aDoc, aTarget, aEventName, aCanBubble, aCancelable,
-                       Trusted::eYes, aDefaultAction, ChromeOnlyDispatch::eYes);
+                       Composed::eDefault, Trusted::eYes, aDefaultAction,
+                       ChromeOnlyDispatch::eYes);
 }
 
 /* static */
diff --git a/dom/base/nsContentUtils.h b/dom/base/nsContentUtils.h
index bc3a8f76b0d7..299c61427bbc 100644
--- a/dom/base/nsContentUtils.h
+++ b/dom/base/nsContentUtils.h
@@ -203,6 +203,7 @@ class nsContentUtils
   typedef mozilla::dom::Element Element;
   typedef mozilla::Cancelable Cancelable;
   typedef mozilla::CanBubble CanBubble;
+  typedef mozilla::Composed Composed;
   typedef mozilla::ChromeOnlyDispatch ChromeOnlyDispatch;
   typedef mozilla::EventMessage EventMessage;
   typedef mozilla::TimeDuration TimeDuration;
@@ -1345,6 +1346,7 @@ public:
    * @param aEventName     The name of the event.
    * @param aCanBubble     Whether the event can bubble.
    * @param aCancelable    Is the event cancelable.
+   * @param aCopmosed      Is the event composed.
    * @param aDefaultAction Set to true if default action should be taken,
    *                       see EventTarget::DispatchEvent.
    */
@@ -1353,8 +1355,21 @@ public:
                                        const nsAString& aEventName,
                                        CanBubble,
                                        Cancelable,
+                                       Composed aComposed = Composed::eDefault,
                                        bool* aDefaultAction = nullptr);
 
+  static nsresult DispatchTrustedEvent(nsIDocument* aDoc,
+                                       nsISupports* aTarget,
+                                       const nsAString& aEventName,
+                                       CanBubble aCanBubble,
+                                       Cancelable aCancelable,
+                                       bool* aDefaultAction)
+  {
+    return DispatchTrustedEvent(aDoc, aTarget, aEventName,
+                                aCanBubble, aCancelable,
+                                Composed::eDefault, aDefaultAction);
+  }
+
   /**
    * This method creates and dispatches a trusted event using an event message.
    * @param aDoc           The document which will be used to create the event.
@@ -3339,6 +3354,7 @@ private:
                                 const nsAString& aEventName,
                                 CanBubble,
                                 Cancelable,
+                                Composed,
                                 Trusted,
                                 bool* aDefaultAction = nullptr,
                                 ChromeOnlyDispatch = ChromeOnlyDispatch::eNo);
diff --git a/dom/events/Event.cpp b/dom/events/Event.cpp
index 663716ac3973..900929cffc1b 100644
--- a/dom/events/Event.cpp
+++ b/dom/events/Event.cpp
@@ -491,7 +491,8 @@ Event::EnsureWebAccessibleRelatedTarget(EventTarget* aRelatedTarget)
 void
 Event::InitEvent(const nsAString& aEventTypeArg,
                  mozilla::CanBubble aCanBubbleArg,
-                 mozilla::Cancelable aCancelableArg)
+                 mozilla::Cancelable aCancelableArg,
+                 mozilla::Composed aComposedArg)
 {
   // Make sure this event isn't already being dispatched.
   NS_ENSURE_TRUE_VOID(!mEvent->mFlags.mIsBeingDispatched);
@@ -507,6 +508,9 @@ Event::InitEvent(const nsAString& aEventTypeArg,
 
   mEvent->mFlags.mBubbles = aCanBubbleArg == CanBubble::eYes;
   mEvent->mFlags.mCancelable = aCancelableArg == Cancelable::eYes;
+  if (aComposedArg != Composed::eDefault) {
+    mEvent->mFlags.mComposed = aComposedArg == Composed::eYes;
+  }
 
   mEvent->mFlags.mDefaultPrevented = false;
   mEvent->mFlags.mDefaultPreventedByContent = false;
diff --git a/dom/events/Event.h b/dom/events/Event.h
index 7b849c4b8eaa..31f4ae0322a6 100755
--- a/dom/events/Event.h
+++ b/dom/events/Event.h
@@ -158,7 +158,8 @@ public:
 
   void InitEvent(const nsAString& aEventTypeArg,
                  mozilla::CanBubble,
-                 mozilla::Cancelable);
+                 mozilla::Cancelable,
+                 mozilla::Composed = mozilla::Composed::eDefault);
 
   void SetTarget(EventTarget* aTarget);
   virtual void DuplicatePrivateData();
diff --git a/dom/events/PendingFullscreenEvent.h b/dom/events/PendingFullscreenEvent.h
index 673507a024bd..9eb35d0aa0a7 100644
--- a/dom/events/PendingFullscreenEvent.h
+++ b/dom/events/PendingFullscreenEvent.h
@@ -52,7 +52,7 @@ public:
     }
     Unused << nsContentUtils::DispatchTrustedEvent(
       mDocument, mDocument, name,
-      CanBubble::eYes, Cancelable::eNo, nullptr);
+      CanBubble::eYes, Cancelable::eNo, Composed::eYes);
   }
 
 private: