Bug 1504365 - Clear weak pointers in shutdown observers. r=erahm

Differential Revision: https://phabricator.services.mozilla.com/D12348

--HG--
extra : moz-landing-system : lando

dom/html/TextTrackManager.cpp

@@ -31,6 +31,13 @@ namespace dom {
 
 NS_IMPL_ISUPPORTS(TextTrackManager::ShutdownObserverProxy, nsIObserver);
 
+void
+TextTrackManager::ShutdownObserverProxy::Unregister()
+{
+  nsContentUtils::UnregisterShutdownObserver(this);
+  mManager = nullptr;
+}
+
 CompareTextTracks::CompareTextTracks(HTMLMediaElement* aMediaElement)
 {
   mMediaElement = aMediaElement;
@@ -140,7 +147,7 @@ TextTrackManager::TextTrackManager(HTMLMediaElement *aMediaElement)
 TextTrackManager::~TextTrackManager()
 {
   WEBVTT_LOG("%p ~TextTrackManager",this);
-  nsContentUtils::UnregisterShutdownObserver(mShutdownProxy);
+  mShutdownProxy->Unregister();
 }
 
 TextTrackList*

dom/html/TextTrackManager.h

@@ -174,12 +174,16 @@ private:
     {
       MOZ_ASSERT(NS_IsMainThread());
       if (strcmp(aTopic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) == 0) {
-        nsContentUtils::UnregisterShutdownObserver(this);
-        mManager->NotifyShutdown();
+        if (mManager) {
+          mManager->NotifyShutdown();
+        }
+        Unregister();
       }
       return NS_OK;
     }
 
+    void Unregister();
+
   private:
     ~ShutdownObserverProxy() {};
     TextTrackManager* mManager;

gfx/thebes/gfxFT2FontList.cpp

@@ -945,6 +945,15 @@ 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()
     { }
@@ -980,11 +989,7 @@ 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();
     }
 }
 

gfx/thebes/gfxFT2FontList.h

@@ -20,6 +20,7 @@ using mozilla::dom::FontListEntry;
 class FontNameCache;
 typedef struct FT_FaceRec_* FT_Face;
 class nsZipArchive;
+class WillShutdownObserver;
 
 class FT2FontEntry : public gfxFontEntry
 {
@@ -200,7 +201,8 @@ protected:
 private:
     mozilla::UniquePtr<FontNameCache> mFontNameCache;
     int64_t mJarModifiedTime;
-    nsCOMPtr<nsIObserver> mObserver;
+    RefPtr<WillShutdownObserver> mObserver;
+
 };
 
 #endif /* GFX_FT2FONTLIST_H */