Bug 1777553 - Use a weak pres context reference in nsMenuItemIconX....

Bug 1777553 - Use a weak pres context reference in nsMenuItemIconX. r=mac-reviewers,spohl, a=dmeehan

This is the only thing from the regressing patch that could potentially
cause this macOS leak, realistically. I don't think the leak is
super-worrisome, likely we just shut down the browser before the image
load finishes.

Differential Revision: https://phabricator.services.mozilla.com/D151368

widget/cocoa/nsMenuItemIconX.h

@@ -13,6 +13,7 @@
 #import <Cocoa/Cocoa.h>
 
 #include "mozilla/widget/IconLoader.h"
+#include "mozilla/WeakPtr.h"
 
 class nsIconLoaderService;
 class nsIURI;
@@ -62,7 +63,7 @@ class nsMenuItemIconX final : public mozilla::widget::IconLoader::Listener {
   Listener* mListener;            // [weak]
   nsIntRect mImageRegionRect;
   RefPtr<const mozilla::ComputedStyle> mComputedStyle;
-  RefPtr<nsPresContext> mPresContext;
+  mozilla::WeakPtr<nsPresContext> mPresContext;
   NSImage* mIconImage = nil;  // [strong]
   RefPtr<mozilla::widget::IconLoader> mIconLoader;
 };

widget/cocoa/nsMenuItemIconX.mm

@@ -167,10 +167,10 @@ nsresult nsMenuItemIconX::OnComplete(imgIContainer* aImage) {
     [mIconImage release];
     mIconImage = nil;
   }
-
+  RefPtr<nsPresContext> pc = mPresContext.get();
   mIconImage = [[MOZIconHelper iconImageFromImageContainer:aImage
                                                   withSize:NSMakeSize(kIconSize, kIconSize)
-                                               presContext:mPresContext
+                                               presContext:pc
                                              computedStyle:mComputedStyle
                                                    subrect:mImageRegionRect
                                                scaleFactor:0.0f] retain];