Backed out changeset dfcc0494fe8d (bug 1839580) for causing wpt and mochitest failures CLOSED TREE

dom/events/AsyncEventDispatcher.h

@@ -190,11 +190,6 @@ class LoadBlockingAsyncEventDispatcher final : public AsyncEventDispatcher {
     }
   }
 
-  // The static version of AsyncEventDispatcher::RunDOMEventWhenSafe should be
-  // preferred when possible, but for LoadBlockingAsyncEventDispatcher it makes
-  // sense to expose the helper so that the load event is blocked appropriately.
-  using AsyncEventDispatcher::RunDOMEventWhenSafe;
-
   LoadBlockingAsyncEventDispatcher(nsINode* aEventNode, dom::Event* aEvent)
       : AsyncEventDispatcher(aEventNode, aEvent),
         mBlockedDoc(aEventNode->OwnerDoc()) {

layout/style/Loader.cpp

@@ -431,11 +431,7 @@ void SheetLoadData::ScheduleLoadEventIfNeeded() {
   auto* dispatcher = new LoadBlockingAsyncEventDispatcher(
       node, mLoadFailed ? u"error"_ns : u"load"_ns, CanBubble::eNo,
       ChromeOnlyDispatch::eNo);
-  if (mMustNotify) {
-    dispatcher->RunDOMEventWhenSafe();
-  } else {
-    dispatcher->PostDOMEvent();
-  }
+  dispatcher->PostDOMEvent();
 }
 
 nsINode* SheetLoadData::GetRequestingNode() const {
@@ -1569,10 +1565,6 @@ void Loader::NotifyObservers(SheetLoadData& aData, nsresult aStatus) {
     // StyleSheetLoaded callback.
     if (aData.BlocksLoadEvent()) {
       DecrementOngoingLoadCount();
-      if (mPendingLoadCount && mPendingLoadCount == mOngoingLoadCount) {
-        LOG(("  No more loading sheets; starting deferred loads"));
-        StartDeferredLoads();
-      }
     }
   }
   if (!aData.mTitle.IsEmpty() && NS_SUCCEEDED(aStatus)) {
@@ -1602,7 +1594,10 @@ void Loader::NotifyObservers(SheetLoadData& aData, nsresult aStatus) {
     }
   }
 
-  aData.ScheduleLoadEventIfNeeded();
+  if (mPendingLoadCount && mPendingLoadCount == mOngoingLoadCount) {
+    LOG(("  No more loading sheets; starting deferred loads"));
+    StartDeferredLoads();
+  }
 }
 
 /**

layout/style/SharedStyleSheetCache.cpp

@@ -164,6 +164,7 @@ void SharedStyleSheetCache::LoadCompletedInternal(
         doc->PostStyleSheetApplicableStateChangeEvent(*data->mSheet);
       }
     }
+    data->ScheduleLoadEventIfNeeded();
     aDatasToNotify.AppendElement(data);
 
     NS_ASSERTION(!data->mParentData || data->mParentData->mPendingChildren != 0,

layout/style/SheetLoadData.h

@@ -159,8 +159,7 @@ class SheetLoadData final
   // the original function call that started the load has returned.
   // This applies only to observer notifications; load/error events
   // are fired for any SheetLoadData that has a non-null
-  // mOwningNodeBeforeLoadEvent (though mMustNotify is used to avoid an event
-  // loop round-trip in that case).
+  // mOwningNodeBeforeLoadEvent.
   bool mMustNotify : 1;
 
   // mWasAlternate is true if the sheet was an alternate when the load data was