b=454735 Make gfxFont more tolerant to shutdown of the gfxFontCache r=roc

gfx/thebes/public/gfxFont.h

@@ -454,9 +454,8 @@ public:
         --mRefCnt;
         NS_LOG_RELEASE(this, mRefCnt, "gfxFont");
         if (mRefCnt == 0) {
-            // Don't delete just yet; return the object to the cache for
-            // possibly recycling within some time limit
-            gfxFontCache::GetCache()->NotifyReleased(this);
+            NotifyReleased();
+            // |this| may have been deleted.
             return 0;
         }
         return mRefCnt;
@@ -467,8 +466,21 @@ public:
 protected:
     nsAutoRefCnt mRefCnt;
 
-public:
+    void NotifyReleased() {
+        gfxFontCache *cache = gfxFontCache::GetCache();
+        if (cache) {
+            // Don't delete just yet; return the object to the cache for
+            // possibly recycling within some time limit
+            cache->NotifyReleased(this);
+        } else {
+            // The cache may have already been shut down.
+            delete this;
+        }
+    }
+
     gfxFont(gfxFontEntry *aFontEntry, const gfxFontStyle *aFontStyle);
+
+public:
     virtual ~gfxFont();
 
     const nsString& GetName() const { return mFontEntry->Name(); }
@@ -637,7 +649,6 @@ public:
 protected:
     nsRefPtr<gfxFontEntry> mFontEntry;
 
-    // The family name of the font
     PRPackedBool               mIsValid;
     nsExpirationState          mExpirationState;
     gfxFontStyle               mStyle;
@@ -1480,9 +1491,10 @@ private:
 };
 
 class THEBES_API gfxFontGroup : public gfxTextRunFactory {
-public:
+protected:
     gfxFontGroup(const nsAString& aFamilies, const gfxFontStyle *aStyle);
 
+public:
     virtual ~gfxFontGroup() {
         mFonts.Clear();
     }