Backed out 2 changesets (bug 1488871) for failures on browser_windowopen.js. CLOSED TREE

Backed out changeset 078929426a6e (bug 1488871)
Backed out changeset 39b3a22e2552 (bug 1488871)

browser/base/content/test/performance/browser_windowopen.js

@@ -47,17 +47,6 @@ if (Services.appinfo.OS == "WINNT" || Services.appinfo.OS == "Darwin") {
   );
 }
 
-// We'll assume the changes we are seeing are due to this focus change if
-// there are at least 5 areas that changed near the top of the screen, or if
-// the toolbar background is involved on OSX, but will only ignore this once.
-function isLikelyFocusChange(rects) {
-  if (rects.length > 5 && rects.every(r => r.y2 < 100))
-    return true;
-  if (Services.appinfo.OS == "Darwin" && rects.length == 2 && rects.every(r => r.y1 == 0 && r.h == 33))
-    return true;
-  return false;
-}
-
 /*
  * This test ensures that there are no unexpected
  * uninterruptible reflows or flickering areas when opening new windows.
@@ -82,7 +71,11 @@ add_task(async function() {
       filter(rects, frame, previousFrame) {
         // The first screenshot we get in OSX / Windows shows an unfocused browser
         // window for some reason. See bug 1445161.
-        if (!alreadyFocused && isLikelyFocusChange(rects)) {
+        //
+        // We'll assume the changes we are seeing are due to this focus change if
+        // there are at least 5 areas that changed near the top of the screen, but
+        // will only ignore this once (hence the alreadyFocused variable).
+        if (!alreadyFocused && rects.length > 5 && rects.every(r => r.y2 < 100)) {
           alreadyFocused = true;
           todo(false,
                "bug 1445161 - the window should be focused at first paint, " +

layout/generic/nsGfxScrollFrame.cpp

@@ -4526,12 +4526,6 @@ ScrollFrameHelper::FireScrollPortEvent()
   nsSize scrollportSize = mScrollPort.Size();
   nsSize childSize = GetScrolledRect().Size();
 
-  // TODO(emilio): why do we need the whole WillPaintObserver infrastructure and
-  // can't use AddScriptRunner & co? I guess it made sense when we used
-  // WillPaintObserver for scroll events too, or when this used to flush.
-  //
-  // Should we remove this?
-
   bool newVerticalOverflow = childSize.height > scrollportSize.height;
   bool vertChanged = mVerticalOverflow != newVerticalOverflow;
 
@@ -5093,6 +5087,10 @@ ScrollFrameHelper::PostScrollEvent()
 NS_IMETHODIMP
 ScrollFrameHelper::AsyncScrollPortEvent::Run()
 {
+  if (mHelper) {
+    mHelper->mOuter->PresContext()->Document()->
+      FlushPendingNotifications(FlushType::InterruptibleLayout);
+  }
   return mHelper ? mHelper->FireScrollPortEvent() : NS_OK;
 }