diff --git a/dom/base/nsIScriptGlobalObject.h b/dom/base/nsIScriptGlobalObject.h
index ec7a241df2d6..2a4e19428c71 100644
--- a/dom/base/nsIScriptGlobalObject.h
+++ b/dom/base/nsIScriptGlobalObject.h
@@ -15,12 +15,6 @@
 class nsIScriptContext;
 class nsIScriptGlobalObject;
 
-namespace mozilla {
-namespace dom {
-class ErrorEventInit;
-} // namespace dom
-} // namespace mozilla
-
 // A helper function for nsIScriptGlobalObject implementations to use
 // when handling a script error.  Generally called by the global when a context
 // notifies it of an error via nsIScriptGlobalObject::HandleScriptError.
@@ -28,13 +22,13 @@ class ErrorEventInit;
 // aStatus will be filled in with the status.
 bool
 NS_HandleScriptError(nsIScriptGlobalObject *aScriptGlobal,
-                     const mozilla::dom::ErrorEventInit &aErrorEvent,
+                     mozilla::InternalScriptErrorEvent *aErrorEvent,
                      nsEventStatus *aStatus);
 
 
 #define NS_ISCRIPTGLOBALOBJECT_IID \
-{ 0x6995e1ff, 0x9fc5, 0x44a7, \
- { 0xbd, 0x7c, 0xe7, 0xcd, 0x44, 0x47, 0x22, 0x87 } }
+{ 0x30c64680, 0x909a, 0x4435, \
+  { 0x90, 0x3b, 0x29, 0x3e, 0xb5, 0x5d, 0xc7, 0xa0 } }
 
 /**
  * The global object which keeps a script context for each supported script
@@ -80,9 +74,9 @@ public:
    * Handle a script error.  Generally called by a script context.
    */
   virtual nsresult HandleScriptError(
-                     const mozilla::dom::ErrorEventInit &aErrorEventInit,
+                     mozilla::InternalScriptErrorEvent *aErrorEvent,
                      nsEventStatus *aEventStatus) {
-    NS_ENSURE_STATE(NS_HandleScriptError(this, aErrorEventInit, aEventStatus));
+    NS_ENSURE_STATE(NS_HandleScriptError(this, aErrorEvent, aEventStatus));
     return NS_OK;
   }
 
diff --git a/dom/base/nsJSEnvironment.cpp b/dom/base/nsJSEnvironment.cpp
index cbd78e7a5e01..ade9559644c3 100644
--- a/dom/base/nsJSEnvironment.cpp
+++ b/dom/base/nsJSEnvironment.cpp
@@ -52,8 +52,6 @@
 #include "nsGlobalWindow.h"
 #include "nsScriptNameSpaceManager.h"
 #include "StructuredCloneTags.h"
-#include "mozilla/AutoRestore.h"
-#include "mozilla/dom/ErrorEvent.h"
 #include "mozilla/dom/ImageData.h"
 #include "mozilla/dom/ImageDataBinding.h"
 #include "nsAXPCNativeCallContext.h"
@@ -314,7 +312,7 @@ private:
 // XXXmarkh - This function is mis-placed!
 bool
 NS_HandleScriptError(nsIScriptGlobalObject *aScriptGlobal,
-                     const ErrorEventInit &aErrorEventInit,
+                     InternalScriptErrorEvent *aErrorEvent,
                      nsEventStatus *aStatus)
 {
   bool called = false;
@@ -327,17 +325,11 @@ NS_HandleScriptError(nsIScriptGlobalObject *aScriptGlobal,
     static int32_t errorDepth; // Recursion prevention
     ++errorDepth;
 
-    if (errorDepth < 2) {
+    if (presContext && errorDepth < 2) {
       // Dispatch() must be synchronous for the recursion block
       // (errorDepth) to work.
-      nsRefPtr<ErrorEvent> event =
-        ErrorEvent::Constructor(static_cast<nsGlobalWindow*>(win.get()),
-                                NS_LITERAL_STRING("error"),
-                                aErrorEventInit);
-      event->SetTrusted(true);
-
-      nsEventDispatcher::DispatchDOMEvent(win, nullptr, event, presContext,
-                                          aStatus);
+      nsEventDispatcher::Dispatch(win, presContext, aErrorEvent, nullptr,
+                                  aStatus);
       called = true;
     }
     --errorDepth;
@@ -452,47 +444,44 @@ public:
       if (docShell &&
           !JSREPORT_IS_WARNING(mFlags) &&
           !sHandlingScriptError) {
-        AutoRestore<bool> recursionGuard(sHandlingScriptError);
-        sHandlingScriptError = true;
+        sHandlingScriptError = true; // Recursion prevention
 
         nsRefPtr<nsPresContext> presContext;
         docShell->GetPresContext(getter_AddRefs(presContext));
 
-        ErrorEventInit init;
-        init.mCancelable = true;
-        init.mFilename = mFileName;
-        init.mBubbles = true;
+        if (presContext) {
+          InternalScriptErrorEvent errorevent(true, NS_LOAD_ERROR);
 
-        nsCOMPtr<nsIScriptObjectPrincipal> sop(do_QueryInterface(win));
-        NS_ENSURE_STATE(sop);
-        nsIPrincipal* p = sop->GetPrincipal();
-        NS_ENSURE_STATE(p);
+          errorevent.fileName = mFileName.get();
 
-        bool sameOrigin = !mOriginPrincipal;
+          nsCOMPtr<nsIScriptObjectPrincipal> sop(do_QueryInterface(win));
+          NS_ENSURE_STATE(sop);
+          nsIPrincipal* p = sop->GetPrincipal();
+          NS_ENSURE_STATE(p);
 
-        if (p && !sameOrigin) {
-          if (NS_FAILED(p->Subsumes(mOriginPrincipal, &sameOrigin))) {
-            sameOrigin = false;
+          bool sameOrigin = !mOriginPrincipal;
+
+          if (p && !sameOrigin) {
+            if (NS_FAILED(p->Subsumes(mOriginPrincipal, &sameOrigin))) {
+              sameOrigin = false;
+            }
           }
+
+          NS_NAMED_LITERAL_STRING(xoriginMsg, "Script error.");
+          if (sameOrigin) {
+            errorevent.errorMsg = mErrorMsg.get();
+            errorevent.lineNr = mLineNumber;
+          } else {
+            NS_WARNING("Not same origin error!");
+            errorevent.errorMsg = xoriginMsg.get();
+            errorevent.lineNr = 0;
+          }
+
+          nsEventDispatcher::Dispatch(win, presContext, &errorevent, nullptr,
+                                      &status);
         }
 
-        NS_NAMED_LITERAL_STRING(xoriginMsg, "Script error.");
-        if (sameOrigin) {
-          init.mMessage = mErrorMsg;
-          init.mLineno = mLineNumber;
-        } else {
-          NS_WARNING("Not same origin error!");
-          init.mMessage = xoriginMsg;
-          init.mLineno = 0;
-        }
-
-        nsRefPtr<ErrorEvent> event =
-          ErrorEvent::Constructor(static_cast<nsGlobalWindow*>(win.get()),
-                                  NS_LITERAL_STRING("error"), init);
-        event->SetTrusted(true);
-
-        nsEventDispatcher::DispatchDOMEvent(win, nullptr, event, presContext,
-                                            &status);
+        sHandlingScriptError = false;
       }
     }
 
diff --git a/dom/base/test/mochitest.ini b/dom/base/test/mochitest.ini
index e236d73ac369..81a81fd6d9a4 100644
--- a/dom/base/test/mochitest.ini
+++ b/dom/base/test/mochitest.ini
@@ -9,7 +9,6 @@ support-files =
 [test_Image_constructor.html]
 [test_appname_override.html]
 [test_bug913761.html]
-[test_clearTimeoutIntervalNoArg.html]
 [test_constructor-assignment.html]
 [test_constructor.html]
 [test_document.all_unqualified.html]
diff --git a/dom/base/test/test_clearTimeoutIntervalNoArg.html b/dom/base/test/test_clearTimeoutIntervalNoArg.html
deleted file mode 100644
index e1d60022fb27..000000000000
--- a/dom/base/test/test_clearTimeoutIntervalNoArg.html
+++ /dev/null
@@ -1,14 +0,0 @@
-<!DOCTYPE html>
-<meta charset=utf-8>
-<title>Test for clearTimeout/clearInterval with no arguments not throwing</title>
-<script src="/resources/testharness.js"></script>
-<script src="/resources/testharnessreport.js"></script>
-<div id="log"></div>
-<script>
-test(function() {
-  clearTimeout();
-}, "clearTimeout with no args should not throw ");
-test(function() {
-  clearInterval();
-}, "clearInterval with no args should not throw ");
-</script>
diff --git a/dom/bindings/Codegen.py b/dom/bindings/Codegen.py
index 0f116cfde065..897afd446b4f 100644
--- a/dom/bindings/Codegen.py
+++ b/dom/bindings/Codegen.py
@@ -11992,17 +11992,9 @@ class CGEventClass(CGBindingImplClass):
               "parentType": self.parentType
             })
 
-        className = descriptor.nativeType.split('::')[-1]
-        asConcreteTypeMethod = ClassMethod("As%s" % className,
-                                           "%s*" % className,
-                                           [],
-                                           virtual=True,
-                                           body="return this;",
-                                           breakAfterReturnDecl=" ")
-
-        CGClass.__init__(self, className,
+        CGClass.__init__(self, descriptor.nativeType.split('::')[-1],
                          bases=[ClassBase(self.parentType)],
-                         methods=[asConcreteTypeMethod]+self.methodDecls,
+                         methods=self.methodDecls,
                          members=members,
                          extradeclarations=baseDeclarations)
 
diff --git a/dom/events/nsDOMEvent.cpp b/dom/events/nsDOMEvent.cpp
index 659a289579d1..f638c0740e13 100644
--- a/dom/events/nsDOMEvent.cpp
+++ b/dom/events/nsDOMEvent.cpp
@@ -764,6 +764,15 @@ nsDOMEvent::GetEventPopupControlState(WidgetEvent* aEvent)
       }
     }
     break;
+  case NS_SCRIPT_ERROR_EVENT :
+    switch(aEvent->message) {
+    case NS_LOAD_ERROR :
+      // Any error event will allow popups, if enabled in the pref.
+      if (::PopupAllowedForEvent("error"))
+        abuse = openControlled;
+      break;
+    }
+    break;
   case NS_FORM_EVENT :
     // For these following events only allow popups if they're
     // triggered while handling user input. See
diff --git a/dom/events/nsDOMEvent.h b/dom/events/nsDOMEvent.h
index c08fb65a6e28..5f4993b21cbc 100644
--- a/dom/events/nsDOMEvent.h
+++ b/dom/events/nsDOMEvent.h
@@ -27,7 +27,6 @@ class nsPresContext;
 namespace mozilla {
 namespace dom {
 class EventTarget;
-class ErrorEvent;
 }
 }
 
@@ -91,11 +90,6 @@ public:
     return mozilla::dom::EventBinding::Wrap(aCx, aScope, this);
   }
 
-  virtual mozilla::dom::ErrorEvent* AsErrorEvent()
-  {
-    return nullptr;
-  }
-
   // nsIDOMEvent Interface
   NS_DECL_NSIDOMEVENT
 
diff --git a/dom/events/nsJSEventListener.cpp b/dom/events/nsJSEventListener.cpp
index 0ca3ce277dad..62fceedbdb38 100644
--- a/dom/events/nsJSEventListener.cpp
+++ b/dom/events/nsJSEventListener.cpp
@@ -19,7 +19,6 @@
 #include "nsDOMJSUtils.h"
 #include "mozilla/ContentEvents.h"
 #include "mozilla/Likely.h"
-#include "mozilla/dom/ErrorEvent.h"
 #include "mozilla/dom/UnionTypes.h"
 #include "nsDOMEvent.h"
 
@@ -168,16 +167,19 @@ nsJSEventListener::HandleEvent(nsIDOMEvent* aEvent)
     Optional<uint32_t> columnNumber;
 
     NS_ENSURE_TRUE(aEvent, NS_ERROR_UNEXPECTED);
-    ErrorEvent* scriptEvent = aEvent->InternalDOMEvent()->AsErrorEvent();
-    if (scriptEvent) {
-      scriptEvent->GetMessage(errorMsg);
+    InternalScriptErrorEvent* scriptEvent =
+      aEvent->GetInternalNSEvent()->AsScriptErrorEvent();
+    if (scriptEvent &&
+        (scriptEvent->message == NS_LOAD_ERROR ||
+         scriptEvent->typeString.EqualsLiteral("error"))) {
+      errorMsg = scriptEvent->errorMsg;
       msgOrEvent.SetAsString().SetData(errorMsg.Data(), errorMsg.Length());
 
-      scriptEvent->GetFilename(file);
+      file = scriptEvent->fileName;
       fileName = &file;
 
       lineNumber.Construct();
-      lineNumber.Value() = scriptEvent->Lineno();
+      lineNumber.Value() = scriptEvent->lineNr;
     } else {
       msgOrEvent.SetAsEvent() = aEvent->InternalDOMEvent();
     }
diff --git a/dom/events/test/error_event_worker.js b/dom/events/test/error_event_worker.js
deleted file mode 100644
index 9f6e0e4bd266..000000000000
--- a/dom/events/test/error_event_worker.js
+++ /dev/null
@@ -1,15 +0,0 @@
- addEventListener("error", function(e) {
-     var obj = {};
-     for (var prop of ["message", "filename", "lineno"]) {
-       obj[prop] = e[prop]
-     }
-     obj.type = "event";
-     postMessage(obj);
-});
-onerror = function(message, filename, lineno) {
-  var obj = { message: message, filename: filename, lineno: lineno,
-	      type: "callback" }
-  postMessage(obj);
-  return false;
-}
-throw new Error("workerhello");
diff --git a/dom/events/test/mochitest.ini b/dom/events/test/mochitest.ini
index ee460d9126ff..f5facec8a960 100644
--- a/dom/events/test/mochitest.ini
+++ b/dom/events/test/mochitest.ini
@@ -6,7 +6,6 @@ support-files =
   bug426082.html
   bug457672.html
   bug656379-1.html
-  error_event_worker.js
   empty.js
   window_bug493251.html
   window_bug659071.html
@@ -131,7 +130,6 @@ skip-if = toolkit == 'android' #CRASH_DUMP, RANDOM
 [test_draggableprop.html]
 skip-if = toolkit == 'android' #CRASH_DUMP, RANDOM
 [test_dragstart.html]
-[test_error_events.html]
 skip-if = toolkit == 'android' #TIMED_OUT
 [test_eventctors.html]
 skip-if = toolkit == 'android' #CRASH_DUMP, RANDOM
diff --git a/dom/events/test/test_error_events.html b/dom/events/test/test_error_events.html
deleted file mode 100644
index 7591debd62cd..000000000000
--- a/dom/events/test/test_error_events.html
+++ /dev/null
@@ -1,62 +0,0 @@
-<!DOCTYPE html>
-<meta charset=utf-8>
-<title>Test for error events being ErrorEvent</title>
-<script src="/resources/testharness.js"></script>
-<script src="/resources/testharnessreport.js"></script>
-<div id="log"></div>
-<script>
-  var errorEvent;
-  var file;
-  var line;
-  var msg;
-  window.addEventListener("error", function errorListener(e) {
-    window.removeEventListener("error", errorListener);
-    errorEvent = e;
-  });
-  var oldOnerror = window.onerror;
-  window.onerror = function(message, filename, lineno) {
-    window.onerror = oldOnerror;
-    file = filename;
-    line = lineno;
-    msg = message;
-  }
-  throw new Error("hello");
-</script>
-<script>
-  generate_tests(assert_equals, [
-    [ "Event filename", errorEvent.filename, location.href ],
-    [ "Callback filename", file, location.href ],
-    [ "Event line number", errorEvent.lineno, 23 ],
-    [ "Callback line number", line, 23 ],
-    [ "Event message", errorEvent.message, "Error: hello" ],
-    [ "Callback message", msg, "Error: hello" ]
-  ]);
-</script>
-<script>
-  var workerLocation = location.protocol + "//" + location.host +
-    location.pathname.replace("test_error_events.html", "error_event_worker.js");
-  var eventFileTest = async_test("Worker event filename");
-  var eventLineTest = async_test("Worker event line number");
-  var eventMessageTest = async_test("Worker event message");
-  var callbackFileTest = async_test("Worker callback filename");
-  var callbackLineTest = async_test("Worker callback line number");
-  var callbackMessageTest = async_test("Worker callback message");
-  var w = new Worker("error_event_worker.js");
-  w.addEventListener("message", function(msg) {
-    if (msg.data.type == "event") {
-      eventFileTest.step(function() { assert_equals(msg.data.filename, workerLocation); });
-      eventFileTest.done();
-      eventLineTest.step(function() { assert_equals(msg.data.lineno, 15); });
-      eventLineTest.done();
-      eventMessageTest.step(function() { assert_equals(msg.data.message, "Error: workerhello"); });
-      eventMessageTest.done();
-    } else {
-      callbackFileTest.step(function() { assert_equals(msg.data.filename, workerLocation); });
-      callbackFileTest.done();
-      callbackLineTest.step(function() { assert_equals(msg.data.lineno, 15); });
-      callbackLineTest.done();
-      callbackMessageTest.step(function() { assert_equals(msg.data.message, "Error: workerhello"); });
-      callbackMessageTest.done();
-    }
-  });
-</script>
diff --git a/dom/indexedDB/IDBRequest.cpp b/dom/indexedDB/IDBRequest.cpp
index 81dd71aa64f8..e57957573358 100644
--- a/dom/indexedDB/IDBRequest.cpp
+++ b/dom/indexedDB/IDBRequest.cpp
@@ -9,7 +9,6 @@
 #include "nsIScriptContext.h"
 
 #include "mozilla/ContentEvents.h"
-#include "mozilla/dom/ErrorEventBinding.h"
 #include "mozilla/dom/IDBOpenDBRequestBinding.h"
 #include "mozilla/dom/UnionTypes.h"
 #include "nsComponentManagerUtils.h"
@@ -301,10 +300,10 @@ IDBRequest::CaptureCaller()
 }
 
 void
-IDBRequest::FillScriptErrorEvent(ErrorEventInit& aEventInit) const
+IDBRequest::FillScriptErrorEvent(InternalScriptErrorEvent* aEvent) const
 {
-  aEventInit.mLineno = mLineNo;
-  aEventInit.mFilename = mFilename;
+  aEvent->lineNr = mLineNo;
+  aEvent->fileName = mFilename.get();
 }
 
 mozilla::dom::IDBRequestReadyState
diff --git a/dom/indexedDB/IDBRequest.h b/dom/indexedDB/IDBRequest.h
index e9dc923c3cb1..1f3486d88a4b 100644
--- a/dom/indexedDB/IDBRequest.h
+++ b/dom/indexedDB/IDBRequest.h
@@ -25,7 +25,6 @@ class nsPIDOMWindow;
 namespace mozilla {
 namespace dom {
 class OwningIDBObjectStoreOrIDBIndexOrIDBCursor;
-class ErrorEventInit;
 }
 }
 
@@ -102,7 +101,7 @@ public:
 
   void CaptureCaller();
 
-  void FillScriptErrorEvent(ErrorEventInit& aEventInit) const;
+  void FillScriptErrorEvent(mozilla::InternalScriptErrorEvent* aEvent) const;
 
   bool
   IsPending() const
diff --git a/dom/indexedDB/IndexedDatabaseManager.cpp b/dom/indexedDB/IndexedDatabaseManager.cpp
index 3fea95707039..b8f9336fd3fc 100644
--- a/dom/indexedDB/IndexedDatabaseManager.cpp
+++ b/dom/indexedDB/IndexedDatabaseManager.cpp
@@ -17,7 +17,6 @@
 #include "mozilla/ClearOnShutdown.h"
 #include "mozilla/CondVar.h"
 #include "mozilla/ContentEvents.h"
-#include "mozilla/dom/ErrorEventBinding.h"
 #include "mozilla/dom/quota/OriginOrPatternString.h"
 #include "mozilla/dom/quota/QuotaManager.h"
 #include "mozilla/dom/quota/Utilities.h"
@@ -341,18 +340,19 @@ IndexedDatabaseManager::FireWindowOnError(nsPIDOMWindow* aOwner,
     error->GetName(errorName);
   }
 
-  ErrorEventInit init;
-  request->FillScriptErrorEvent(init);
+  mozilla::InternalScriptErrorEvent event(true, NS_LOAD_ERROR);
+  request->FillScriptErrorEvent(&event);
+  NS_ABORT_IF_FALSE(event.fileName,
+                    "FillScriptErrorEvent should give us a non-null string "
+                    "for our error's fileName");
 
-  init.mMessage = errorName;
-  init.mCancelable = true;
-  init.mBubbles = true;
+  event.errorMsg = errorName.get();
 
   nsCOMPtr<nsIScriptGlobalObject> sgo(do_QueryInterface(aOwner));
   NS_ASSERTION(sgo, "How can this happen?!");
 
   nsEventStatus status = nsEventStatus_eIgnore;
-  if (NS_FAILED(sgo->HandleScriptError(init, &status))) {
+  if (NS_FAILED(sgo->HandleScriptError(&event, &status))) {
     NS_WARNING("Failed to dispatch script error event");
     status = nsEventStatus_eIgnore;
   }
@@ -368,8 +368,8 @@ IndexedDatabaseManager::FireWindowOnError(nsPIDOMWindow* aOwner,
   NS_ENSURE_SUCCESS(rv, rv);
 
   if (NS_FAILED(scriptError->InitWithWindowID(errorName,
-                                              init.mFilename,
-                                              EmptyString(), init.mLineno,
+                                              nsDependentString(event.fileName),
+                                              EmptyString(), event.lineNr,
                                               0, 0,
                                               "IndexedDB",
                                               aOwner->WindowID()))) {
diff --git a/dom/webidl/Window.webidl b/dom/webidl/Window.webidl
index c6d60bcc2ec7..bfd04893c98b 100644
--- a/dom/webidl/Window.webidl
+++ b/dom/webidl/Window.webidl
@@ -88,10 +88,10 @@ Window implements WindowEventHandlers;
 interface WindowTimers {
   [Throws] long setTimeout(Function handler, optional long timeout = 0, any... arguments);
   [Throws] long setTimeout(DOMString handler, optional long timeout = 0, any... unused);
-  [Throws] void clearTimeout(optional long handle = 0);
+  [Throws] void clearTimeout(long handle);
   [Throws] long setInterval(Function handler, optional long timeout, any... arguments);
   [Throws] long setInterval(DOMString handler, optional long timeout, any... unused);
-  [Throws] void clearInterval(optional long handle = 0);
+  [Throws] void clearInterval(long handle);
 };
 Window implements WindowTimers;
 
diff --git a/dom/workers/WorkerPrivate.cpp b/dom/workers/WorkerPrivate.cpp
index 3237073ca069..03cf32eb6efb 100644
--- a/dom/workers/WorkerPrivate.cpp
+++ b/dom/workers/WorkerPrivate.cpp
@@ -1186,16 +1186,16 @@ public:
     // they show up in the error console.
     if (!JSREPORT_IS_WARNING(aFlags)) {
       // First fire an ErrorEvent at the worker.
-      ErrorEventInit init;
-      init.mMessage = aMessage;
-      init.mFilename = aFilename;
-      init.mLineno = aLineNumber;
-      init.mCancelable = true;
-      init.mBubbles = true;
-
       if (aTarget) {
+        ErrorEventInit init;
+        init.mMessage = aMessage;
+        init.mFilename = aFilename;
+        init.mLineno = aLineNumber;
+        init.mCancelable = true;
+
         nsRefPtr<ErrorEvent> event =
           ErrorEvent::Constructor(aTarget, NS_LITERAL_STRING("error"), init);
+
         event->SetTrusted(true);
 
         nsEventStatus status = nsEventStatus_eIgnore;
@@ -1219,22 +1219,30 @@ public:
           WorkerGlobalScope* globalTarget = aWorkerPrivate->GlobalScope();
           MOZ_ASSERT(target == globalTarget->GetWrapperPreserveColor());
 
-          nsRefPtr<ErrorEvent> event =
-            ErrorEvent::Constructor(aTarget, NS_LITERAL_STRING("error"), init);
-          event->SetTrusted(true);
+          // Icky, we have to fire an InternalScriptErrorEvent...
+          MOZ_ASSERT(!NS_IsMainThread());
+          InternalScriptErrorEvent event(true, NS_USER_DEFINED_EVENT);
+          event.lineNr = aLineNumber;
+          event.errorMsg = aMessage.get();
+          event.fileName = aFilename.get();
+          event.typeString = NS_LITERAL_STRING("error");
 
           nsIDOMEventTarget* target = static_cast<nsIDOMEventTarget*>(globalTarget);
-          if (NS_FAILED(nsEventDispatcher::DispatchDOMEvent(target, nullptr,
-                                                            event, nullptr,
-                                                            &status))) {
+          if (NS_FAILED(nsEventDispatcher::Dispatch(target, nullptr, &event,
+                                                    nullptr, &status))) {
             NS_WARNING("Failed to dispatch worker thread error event!");
             status = nsEventStatus_eIgnore;
           }
         }
         else if ((sgo = nsJSUtils::GetStaticScriptGlobal(target))) {
+          // Icky, we have to fire an InternalScriptErrorEvent...
           MOZ_ASSERT(NS_IsMainThread());
+          InternalScriptErrorEvent event(true, NS_LOAD_ERROR);
+          event.lineNr = aLineNumber;
+          event.errorMsg = aMessage.get();
+          event.fileName = aFilename.get();
 
-          if (NS_FAILED(sgo->HandleScriptError(init, &status))) {
+          if (NS_FAILED(sgo->HandleScriptError(&event, &status))) {
             NS_WARNING("Failed to dispatch main thread error event!");
             status = nsEventStatus_eIgnore;
           }
@@ -3185,15 +3193,13 @@ WorkerPrivateParent<Derived>::BroadcastErrorToSharedWorkers(
     MOZ_ASSERT(sgo);
 
     MOZ_ASSERT(NS_IsMainThread());
-    ErrorEventInit init;
-    init.mLineno = aLineNumber;
-    init.mFilename = aFilename;
-    init.mMessage = aMessage;
-    init.mCancelable = true;
-    init.mBubbles = true;
+    InternalScriptErrorEvent event(true, NS_LOAD_ERROR);
+    event.lineNr = aLineNumber;
+    event.errorMsg = aMessage.BeginReading();
+    event.fileName = aFilename.BeginReading();
 
     nsEventStatus status = nsEventStatus_eIgnore;
-    rv = sgo->HandleScriptError(init, &status);
+    rv = sgo->HandleScriptError(&event, &status);
     if (NS_FAILED(rv)) {
       Throw(cx, rv);
       JS_ReportPendingException(cx);
diff --git a/widget/BasicEvents.h b/widget/BasicEvents.h
index 064b491134bb..8af75df20fec 100644
--- a/widget/BasicEvents.h
+++ b/widget/BasicEvents.h
@@ -49,6 +49,7 @@ enum nsEventStructType
   NS_TOUCH_EVENT,                    // WidgetTouchEvent
 
   // ContentEvents.h
+  NS_SCRIPT_ERROR_EVENT,             // InternalScriptErrorEvent
   NS_SCROLLPORT_EVENT,               // InternalScrollPortEvent
   NS_SCROLLAREA_EVENT,               // InternalScrollAreaEvent
   NS_FORM_EVENT,                     // InternalFormEvent
diff --git a/widget/ContentEvents.h b/widget/ContentEvents.h
index d5b844f488f4..7763927534e9 100644
--- a/widget/ContentEvents.h
+++ b/widget/ContentEvents.h
@@ -19,6 +19,55 @@ class nsIContent;
 
 namespace mozilla {
 
+/******************************************************************************
+ * mozilla::InternalScriptErrorEvent
+ ******************************************************************************/
+
+class InternalScriptErrorEvent : public WidgetEvent
+{
+public:
+  virtual InternalScriptErrorEvent* AsScriptErrorEvent() MOZ_OVERRIDE
+  {
+    return this;
+  }
+
+  InternalScriptErrorEvent(bool aIsTrusted, uint32_t aMessage) :
+    WidgetEvent(aIsTrusted, aMessage, NS_SCRIPT_ERROR_EVENT),
+    lineNr(0), errorMsg(nullptr), fileName(nullptr)
+  {
+  }
+
+  virtual WidgetEvent* Duplicate() const MOZ_OVERRIDE
+  {
+    MOZ_ASSERT(eventStructType == NS_SCRIPT_ERROR_EVENT,
+               "Duplicate() must be overridden by sub class");
+    InternalScriptErrorEvent* result =
+      new InternalScriptErrorEvent(false, message);
+    result->AssignScriptErrorEventData(*this, true);
+    result->mFlags = mFlags;
+    return result;
+  }
+
+
+  int32_t           lineNr;
+  const char16_t*  errorMsg;
+  const char16_t*  fileName;
+
+  // XXX Not tested by test_assign_event_data.html
+  void AssignScriptErrorEventData(const InternalScriptErrorEvent& aEvent,
+                                  bool aCopyTargets)
+  {
+    AssignEventData(aEvent, aCopyTargets);
+
+    lineNr = aEvent.lineNr;
+
+    // We don't copy errorMsg and fileName.  If it's necessary, perhaps, this
+    // should duplicate the characters and free them at destructing.
+    errorMsg = nullptr;
+    fileName = nullptr;
+  }
+};
+
 /******************************************************************************
  * mozilla::InternalScrollPortEvent
  ******************************************************************************/
diff --git a/widget/EventClassList.h b/widget/EventClassList.h
index 6a7f5f144666..27e3afcdd083 100644
--- a/widget/EventClassList.h
+++ b/widget/EventClassList.h
@@ -41,6 +41,7 @@ NS_EVENT_CLASS(Widget, SimpleGestureEvent)
 NS_EVENT_CLASS(Widget, TouchEvent)
 
 // ContentEvents.h
+NS_EVENT_CLASS(Internal, ScriptErrorEvent)
 NS_EVENT_CLASS(Internal, ScrollPortEvent)
 NS_EVENT_CLASS(Internal, ScrollAreaEvent)
 NS_EVENT_CLASS(Internal, FormEvent)
diff --git a/widget/tests/test_assign_event_data.html b/widget/tests/test_assign_event_data.html
index 0c7eec2cf4ca..7aee46b476a3 100644
--- a/widget/tests/test_assign_event_data.html
+++ b/widget/tests/test_assign_event_data.html
@@ -74,6 +74,17 @@ function onEvent(aEvent)
 }
 
 const kTests = [
+  { description: "InternalScriptErrorEvent",
+    targetID: "input-text", eventType: "error",
+    dispatchEvent: function () {
+      return;
+    },
+    canRun: function () {
+      todo(false, "InternalScriptErrorEvent isn't tested");
+      return false;
+    },
+    todoMismatch: [],
+  },
   { description: "InternalScrollPortEvent (overflow, vertical)",
     targetID: "scrollable-div", eventType: "overflow",
     dispatchEvent: function () {