Bug 1376964 - Part 3: Add a generation counter to the user font cache. r=jfkthame

MozReview-Commit-ID: 3zCPC9Pfikc

--HG--
extra : rebase_source : 7186ed96da1b1a6710ef4f5b2f1443ddfe0ddc29

gfx/thebes/gfxUserFontSet.cpp

@@ -1099,7 +1099,10 @@ gfxUserFontSet::GetFamily(const nsAString& aFamilyName)
 ///////////////////////////////////////////////////////////////////////////////
 
 nsTHashtable<gfxUserFontSet::UserFontCache::Entry>*
-    gfxUserFontSet::UserFontCache::sUserFonts = nullptr;
+gfxUserFontSet::UserFontCache::sUserFonts = nullptr;
+
+uint32_t
+gfxUserFontSet::UserFontCache::sGeneration = 0;
 
 NS_IMPL_ISUPPORTS(gfxUserFontSet::UserFontCache::Flusher, nsIObserver)
 
@@ -1233,6 +1236,8 @@ gfxUserFontSet::UserFontCache::CacheFont(gfxFontEntry* aFontEntry)
     sUserFonts->PutEntry(Key(data->mURI, principal, aFontEntry,
                              data->mPrivate));
 
+    ++sGeneration;
+
 #ifdef DEBUG_USERFONT_CACHE
     printf("userfontcache added fontentry: %p\n", aFontEntry);
     Dump();

gfx/thebes/gfxUserFontSet.h

@@ -301,6 +301,10 @@ public:
                                      gfxUserFontEntry* aUserFontEntry,
                                      bool              aPrivate);
 
+        // Generation number that is incremented whenever an entry is added to
+        // the cache.  (Removals don't increment it.)
+        static uint32_t Generation() { return sGeneration; }
+
         // Clear everything so that we don't leak URIs and Principals.
         static void Shutdown();
 
@@ -428,6 +432,8 @@ public:
         };
 
         static nsTHashtable<Entry>* sUserFonts;
+
+        static uint32_t sGeneration;
     };
 
     void SetLocalRulesUsed() {