Backed out changeset 84302aebbe43 (bug 1573813) for failing mochitest jobs on a CLOSED TREE.

widget/gtk/nsWindow.cpp

@@ -6589,22 +6589,11 @@ void nsWindow::SetDrawsInTitlebar(bool aState) {
 }
 
 gint nsWindow::GdkScaleFactor() {
-  // For popup windows with parent window we need to get scale factor of the
-  // parent window. Otherwise the scale factor of the popup is not updated
-  // during it's hidden.
-  GdkWindow* scaledGdkWindow = mGdkWindow;
-  if (mWindowType == eWindowType_popup && mToplevelParentWindow) {
-    scaledGdkWindow = gtk_widget_get_window(GTK_WIDGET(mToplevelParentWindow));
-    // Fallback for windows which parent has been unrealized.
-    if (!scaledGdkWindow) {
-      scaledGdkWindow = mGdkWindow;
-    }
-  }
   // Available as of GTK 3.10+
   static auto sGdkWindowGetScaleFactorPtr =
       (gint(*)(GdkWindow*))dlsym(RTLD_DEFAULT, "gdk_window_get_scale_factor");
-  if (sGdkWindowGetScaleFactorPtr && scaledGdkWindow)
-    return (*sGdkWindowGetScaleFactorPtr)(scaledGdkWindow);
+  if (sGdkWindowGetScaleFactorPtr && mGdkWindow)
+    return (*sGdkWindowGetScaleFactorPtr)(mGdkWindow);
   return ScreenHelperGTK::GetGTKMonitorScaleFactor();
 }