No Issue - Make nsCocoaWindow hold a death grip on its native window …

…until its destructor.

https://bugzilla.mozilla.org/show_bug.cgi?id=1880582

widget/cocoa/nsCocoaWindow.h

@@ -412,8 +412,13 @@ class nsCocoaWindow : public nsBaseWidget, public nsPIWidgetCocoa
   nsIWidget*           mParent;         // if we're a popup, this is our parent [WEAK]
   nsIWidget*           mAncestorLink;   // link to traverse ancestors [WEAK]
   BaseWindow*          mWindow;         // our cocoa window [STRONG]
+  BaseWindow*          mClosedRetainedWindow;  // a second strong reference to our
+  // window upon closing it, held through our destructor. This is useful
+  // to ensure that macOS run loops which reference the window will still
+  // have something to point to even if they don't use proper retain and
+  // release patterns.  
   WindowDelegate*      mDelegate;       // our delegate for processing window msgs [STRONG]
-  RefPtr<nsMenuBarX> mMenuBar;
+  RefPtr<nsMenuBarX>   mMenuBar;
   NSWindow*            mSheetWindowParent; // if this is a sheet, this is the NSWindow it's attached to
   nsChildView*         mPopupContentView; // if this is a popup, this is its content widget
   // if this is a toplevel window, and there is any ongoing fullscreen

widget/cocoa/nsCocoaWindow.mm

@@ -109,6 +109,7 @@ static void RollUpPopups()
 : mParent(nullptr)
 , mAncestorLink(nullptr)
 , mWindow(nil)
+, mClosedRetainedWindow(nil)
 , mDelegate(nil)
 , mSheetWindowParent(nil)
 , mPopupContentView(nil)
@@ -147,6 +148,12 @@ static void RollUpPopups()
   // We want to unhook the delegate here because we don't want events
   // sent to it after this object has been destroyed.
   [mWindow setDelegate:nil];
+  // Closing the window will also release it. Our second reference will
+  // keep it alive through our destructor. Release any reference we might
+  // have from an earlier call to DestroyNativeWindow, then create a new
+  // one.
+  [mClosedRetainedWindow autorelease];
+  mClosedRetainedWindow = [mWindow retain];
   [mWindow close];
   mWindow = nil;
   [mDelegate autorelease];
@@ -181,6 +188,8 @@ static void RollUpPopups()
     DestroyNativeWindow();
   }
 
+  [mClosedRetainedWindow release];
+
   NS_IF_RELEASE(mPopupContentView);
 
   // Deal with the possiblity that we're being destroyed while running modal.