Bug 1535988, backout because bug 1537555, r=backout

dom/html/HTMLFormElement.cpp

@@ -406,8 +406,7 @@ void HTMLFormElement::UnbindFromTree(bool aDeep, bool aNullParent) {
 
 void HTMLFormElement::GetEventTargetParent(EventChainPreVisitor& aVisitor) {
   aVisitor.mWantsWillHandleEvent = true;
-  if (aVisitor.mEvent->IsTrusted() &&
-      aVisitor.mEvent->mOriginalTarget == static_cast<nsIContent*>(this)) {
+  if (aVisitor.mEvent->mOriginalTarget == static_cast<nsIContent*>(this)) {
     uint32_t msg = aVisitor.mEvent->mMessage;
     if (msg == eFormSubmit) {
       if (mGeneratingSubmit) {
@@ -444,8 +443,7 @@ void HTMLFormElement::WillHandleEvent(EventChainPostVisitor& aVisitor) {
 }
 
 nsresult HTMLFormElement::PostHandleEvent(EventChainPostVisitor& aVisitor) {
-  if (aVisitor.mEvent->IsTrusted() &&
-      aVisitor.mEvent->mOriginalTarget == static_cast<nsIContent*>(this)) {
+  if (aVisitor.mEvent->mOriginalTarget == static_cast<nsIContent*>(this)) {
     EventMessage msg = aVisitor.mEvent->mMessage;
     if (msg == eFormSubmit) {
       // let the form know not to defer subsequent submissions

testing/web-platform/tests/html/semantics/forms/the-button-element/button-click-submits.html

@@ -207,20 +207,4 @@ async_test(t => {
 
 }, "clicking the child of a button by dispatching a non-bubbling event should not trigger submit");
 
-async_test(t => {
-  const form = document.createElement("form");
-  const button = document.createElement("button");
-  button.type = "button";
-  button.onclick =
-    function(e) {
-      form.dispatchEvent(new Event("submit"), { bubbles: true});
-    };
-  form.appendChild(button);
-  document.body.appendChild(form);
-
-  button.click();
-
-  t.step_timeout(() => t.done(), 500);
-}, "dispatching submit event should not trigger a submit");
-
 </script>