From aa27f3f5cbed925b572bd11fcb37b95afc44dd0d Mon Sep 17 00:00:00 2001
From: roytam1 <roytam@gmail.com>
Date: Tue, 29 Mar 2022 15:14:36 +0800
Subject: [PATCH] ported from UXP: Clear weak pointers in FT2 font list
 shutdown observers. (f3de54e8)

---
 gfx/thebes/gfxFT2FontList.cpp | 15 ++++++++++-----
 gfx/thebes/gfxFT2FontList.h   |  3 ++-
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/gfx/thebes/gfxFT2FontList.cpp b/gfx/thebes/gfxFT2FontList.cpp
index 49d6cb6bc..8d2639091 100644
--- a/gfx/thebes/gfxFT2FontList.cpp
+++ b/gfx/thebes/gfxFT2FontList.cpp
@@ -812,6 +812,15 @@ public:
         : mFontList(aFontList)
     { }
 
+    void Remove()
+    {
+        nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
+        if (obs) {
+            obs->RemoveObserver(this, NS_XPCOM_WILL_SHUTDOWN_OBSERVER_ID);
+        }
+        mFontList = nullptr;
+    }
+
 protected:
     virtual ~WillShutdownObserver()
     { }
@@ -847,11 +856,7 @@ gfxFT2FontList::gfxFT2FontList()
 gfxFT2FontList::~gfxFT2FontList()
 {
     if (mObserver) {
-        nsCOMPtr<nsIObserverService> obs = services::GetObserverService();
-        if (obs) {
-            obs->RemoveObserver(mObserver, NS_XPCOM_WILL_SHUTDOWN_OBSERVER_ID);
-        }
-        mObserver = nullptr;
+        mObserver->Remove();
     }
 }
 
diff --git a/gfx/thebes/gfxFT2FontList.h b/gfx/thebes/gfxFT2FontList.h
index 63187ba26..9fb566c15 100644
--- a/gfx/thebes/gfxFT2FontList.h
+++ b/gfx/thebes/gfxFT2FontList.h
@@ -19,6 +19,7 @@ using mozilla::dom::FontListEntry;
 class FontNameCache;
 typedef struct FT_FaceRec_* FT_Face;
 class nsZipArchive;
+class WillShutdownObserver;
 
 class FT2FontEntry : public gfxFontEntry
 {
@@ -194,7 +195,7 @@ private:
 
     mozilla::UniquePtr<FontNameCache> mFontNameCache;
     int64_t mJarModifiedTime;
-    nsCOMPtr<nsIObserver> mObserver;
+    RefPtr<WillShutdownObserver> mObserver;
 };
 
 #endif /* GFX_FT2FONTLIST_H */