--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -966,19 +966,16 @@ nsChildView::BackingScaleFactorChanged()
 
   mBackingScaleFactor = newScale;
 
   if (mWidgetListener && !mWidgetListener->GetXULWindow()) {
     nsIPresShell* presShell = mWidgetListener->GetPresShell();
     if (presShell) {
       presShell->BackingScaleFactorChanged();
     }
-    // When the backing scale factor changes, so does our size in device pixels
-    // (though not in display pixels).
-    ReportSizeEvent();
   }
 }
 
 int32_t
 nsChildView::RoundsWidgetCoordinatesTo()
 {
   if (BackingScaleFactor() == 2.0) {
     return 2;

--- a/widget/cocoa/nsCocoaWindow.mm
+++ b/widget/cocoa/nsCocoaWindow.mm
@@ -1699,19 +1699,16 @@ nsCocoaWindow::BackingScaleFactorChanged
   if (!mWidgetListener || mWidgetListener->GetXULWindow()) {
     return;
   }
 
   nsIPresShell* presShell = mWidgetListener->GetPresShell();
   if (presShell) {
     presShell->BackingScaleFactorChanged();
   }
-  // When the backing scale factor changes, so does our size in device pixels
-  // (though not in display pixels).
-  ReportSizeEvent();
 }
 
 int32_t
 nsCocoaWindow::RoundsWidgetCoordinatesTo()
 {
   if (BackingScaleFactor() == 2.0) {
     return 2;
   }