diff --git a/dom/base/nsDOMWindowUtils.cpp b/dom/base/nsDOMWindowUtils.cpp
index 744e6a7dac2e..16e2e358a5d6 100644
--- a/dom/base/nsDOMWindowUtils.cpp
+++ b/dom/base/nsDOMWindowUtils.cpp
@@ -1673,9 +1673,9 @@ nsDOMWindowUtils::GetFullZoom(float* aFullZoom) {
 
 NS_IMETHODIMP
 nsDOMWindowUtils::DispatchDOMEventViaPresShell(nsINode* aTarget, Event* aEvent,
-                                               bool aTrusted, bool* aRetVal) {
+                                               bool* aRetVal) {
   NS_ENSURE_STATE(aEvent);
-  aEvent->SetTrusted(aTrusted);
+  aEvent->SetTrusted(true);
   WidgetEvent* internalEvent = aEvent->WidgetEventPtr();
   NS_ENSURE_STATE(internalEvent);
   nsCOMPtr<nsIContent> content = do_QueryInterface(aTarget);
diff --git a/dom/events/crashtests/1397711.html b/dom/events/crashtests/1397711.html
index 481ecbeda274..3b22ec5c3a4d 100644
--- a/dom/events/crashtests/1397711.html
+++ b/dom/events/crashtests/1397711.html
@@ -7,5 +7,5 @@
     bubbles: true
   });
   let utils = SpecialPowers.getDOMWindowUtils(window);
-  utils.dispatchDOMEventViaPresShell(document.documentElement, e, false);
+  utils.dispatchDOMEventViaPresShell(document.documentElement, e);
 </script>
diff --git a/dom/events/test/test_bug508479.html b/dom/events/test/test_bug508479.html
index 9cf9e22b8a1d..b191a984d9ab 100644
--- a/dom/events/test/test_bug508479.html
+++ b/dom/events/test/test_bug508479.html
@@ -13,7 +13,7 @@ var gGotNotHandlingDrop = false;
 SimpleTest.waitForExplicitFinish();
 
 function fireEvent(target, event) {
-  SpecialPowers.DOMWindowUtils.dispatchDOMEventViaPresShell(target, event, true);
+  SpecialPowers.DOMWindowUtils.dispatchDOMEventViaPresShell(target, event);
 }
 
 function fireDrop(element, shouldAllowDrop, shouldAllowOnlyChromeDrop) {
diff --git a/dom/events/test/test_bug591249.xul b/dom/events/test/test_bug591249.xul
index 22e0ad4fc776..05d109b87bda 100644
--- a/dom/events/test/test_bug591249.xul
+++ b/dom/events/test/test_bug591249.xul
@@ -31,7 +31,7 @@ function completeTest(aBox) {
 function fireEvent(target, event) {
   var win = target.ownerGlobal;
   var utils = win.windowUtils;
-  utils.dispatchDOMEventViaPresShell(target, event, true);
+  utils.dispatchDOMEventViaPresShell(target, event);
 }
 
 function RunTest() {
diff --git a/dom/events/test/test_bug593959.html b/dom/events/test/test_bug593959.html
index 9336167447b1..76008440349d 100644
--- a/dom/events/test/test_bug593959.html
+++ b/dom/events/test/test_bug593959.html
@@ -30,7 +30,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=593959
     var e = document.createEvent("MouseEvent");
     e.initEvent("mousedown", false, false, window, 0, 1, 1, 1, 1,
                 false, false, false, false, 0, null);
-    utils.dispatchDOMEventViaPresShell(document.body, e, true);
+    utils.dispatchDOMEventViaPresShell(document.body, e);
     
     is(document.querySelector("body:active"), document.body, "body should be active!")
     
@@ -41,7 +41,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=593959
     var e2 = ifrwindow.document.createEvent("MouseEvent");
     e2.initEvent("mouseup", false, false, ifrwindow, 0, 1, 1, 1, 1,
                  false, false, false, false, 0, null);
-    utils2.dispatchDOMEventViaPresShell(ifrwindow.document.body, e2, true);
+    utils2.dispatchDOMEventViaPresShell(ifrwindow.document.body, e2);
     
     isnot(document.querySelector("body:active"), document.body, "body shouldn't be active!")
 
diff --git a/dom/interfaces/base/nsIDOMWindowUtils.idl b/dom/interfaces/base/nsIDOMWindowUtils.idl
index ad8468bf1695..4da15bd001e8 100644
--- a/dom/interfaces/base/nsIDOMWindowUtils.idl
+++ b/dom/interfaces/base/nsIDOMWindowUtils.idl
@@ -937,7 +937,8 @@ interface nsIDOMWindowUtils : nsISupports {
   readonly attribute float fullZoom;
 
   /**
-   * Dispatches aEvent via the nsIPresShell object of the window's document.
+   * Dispatches aEvent as a trusted event via the nsIPresShell object of the
+   * window's document.
    * The event is dispatched to aTarget, which should be an object
    * which implements nsIContent interface (#element, #text, etc).
    *
@@ -948,9 +949,9 @@ interface nsIDOMWindowUtils : nsISupports {
    * @note Event handlers won't get aEvent as parameter, but a similar event.
    *       Also, aEvent should not be reused.
    */
+  [can_run_script]
   boolean dispatchDOMEventViaPresShell(in Node aTarget,
-                                       in Event aEvent,
-                                       in boolean aTrusted);
+                                       in Event aEvent);
 
   /**
    * Sets WidgetEvent::mFlags::mOnlyChromeDispatch to true to ensure that
diff --git a/layout/base/tests/test_bug603550.html b/layout/base/tests/test_bug603550.html
index 0df24f28b68c..79bfe22724d2 100644
--- a/layout/base/tests/test_bug603550.html
+++ b/layout/base/tests/test_bug603550.html
@@ -49,7 +49,7 @@ function sendMouseUp(el) {
 
 function fireEvent(target, event) {
   var utils = SpecialPowers.getDOMWindowUtils(window);
-  utils.dispatchDOMEventViaPresShell(target, event, true);
+  utils.dispatchDOMEventViaPresShell(target, event);
 }
 
 function fireDrop(element) {
diff --git a/testing/mochitest/tests/SimpleTest/EventUtils.js b/testing/mochitest/tests/SimpleTest/EventUtils.js
index aebb67fe8850..5387708f5288 100644
--- a/testing/mochitest/tests/SimpleTest/EventUtils.js
+++ b/testing/mochitest/tests/SimpleTest/EventUtils.js
@@ -260,7 +260,7 @@ function sendDragEvent(aEvent, aTarget, aWindow = window) {
   }
 
   var utils = _getDOMWindowUtils(aWindow);
-  return utils.dispatchDOMEventViaPresShell(aTarget, event, true);
+  return utils.dispatchDOMEventViaPresShell(aTarget, event);
 }
 
 /**
diff --git a/toolkit/components/prompts/test/test_bug620145.html b/toolkit/components/prompts/test/test_bug620145.html
index d8da1847e23e..75e21e4a0c86 100644
--- a/toolkit/components/prompts/test/test_bug620145.html
+++ b/toolkit/components/prompts/test/test_bug620145.html
@@ -85,7 +85,7 @@ function dispatchMouseEvent(target, type) {
   e.initEvent(type, false, false, win, 0, 1, 1, 1, 1,
               false, false, false, false, 0, null);
   var utils = SpecialPowers.getDOMWindowUtils(win);
-  utils.dispatchDOMEventViaPresShell(target, e, true);
+  utils.dispatchDOMEventViaPresShell(target, e);
   ok(true, type + " sent to " + target.id);
 }
 
diff --git a/toolkit/components/prompts/test/test_subresources_prompts.html b/toolkit/components/prompts/test/test_subresources_prompts.html
index 69ced062b65e..07f91735a827 100644
--- a/toolkit/components/prompts/test/test_subresources_prompts.html
+++ b/toolkit/components/prompts/test/test_subresources_prompts.html
@@ -193,7 +193,7 @@ function dispatchMouseEvent(target, type) {
   e.initEvent(type, false, false, win, 0, 1, 1, 1, 1,
               false, false, false, false, 0, null);
   var utils = SpecialPowers.getDOMWindowUtils(win);
-  utils.dispatchDOMEventViaPresShell(SpecialPowers.unwrap(target), e, true);
+  utils.dispatchDOMEventViaPresShell(SpecialPowers.unwrap(target), e);
 }
 </script>
 </body>