Bug 1998596 - Don't notify of moves on invisible windows. r=mac-reviewers,mstange

If we're not visible yet, our NSWindow might not have the correct frame
yet, causing us to perform a move to 0, 0, effectively losing the
anchoring.

It's a bit unclear whether we want to react to WindowMoved for popups
anyways, we generally assume we're in control of window positioning
(except for some wayland shenanigans).

Differential Revision: https://phabricator.services.mozilla.com/D273726

Author: emilio

widget/cocoa/nsCocoaWindow.mm

@@ -6549,8 +6549,10 @@ static nsSizeMode GetWindowSizeMode(NSWindow* aWindow, bool aFullScreen) {
     DispatchSizeModeEvent();
   }
 
-  // Dispatch the move event to Gecko
-  NotifyWindowMoved(mBounds.x, mBounds.y);
+  // Dispatch the move event to Gecko, if we're visible.
+  if (IsVisible()) {
+    NotifyWindowMoved(mBounds.x, mBounds.y);
+  }
 
   mInReportMoveEvent = false;