bug 871961 pt 4 - on xpcom-shutdown notification, release any SVG-glyphs documents held by fonts. r=roc

gfx/thebes/gfxFont.cpp

@@ -688,6 +688,15 @@ gfxFontEntry::ReleaseGrFace(gr_face *aFace)
     }
 }
 
+void
+gfxFontEntry::DisconnectSVG()
+{
+    if (mSVGInitialized && mSVGGlyphs) {
+        mSVGGlyphs = nullptr;
+        mSVGInitialized = false;
+    }
+}
+
 void
 gfxFontEntry::CheckForGraphiteTables()
 {
@@ -1393,20 +1402,10 @@ gfxFontCache::MemoryReporter::CollectReports
     return NS_OK;
 }
 
-// Observer for the memory-pressure notification, to trigger
-// flushing of the shaped-word caches
-class MemoryPressureObserver MOZ_FINAL : public nsIObserver,
-                                         public nsSupportsWeakReference
-{
-public:
-    NS_DECL_ISUPPORTS
-    NS_DECL_NSIOBSERVER
-};
-
-NS_IMPL_ISUPPORTS2(MemoryPressureObserver, nsIObserver, nsISupportsWeakReference)
+NS_IMPL_ISUPPORTS1(gfxFontCache::Observer, nsIObserver)
 
 NS_IMETHODIMP
-MemoryPressureObserver::Observe(nsISupports *aSubject,
+gfxFontCache::Observer::Observe(nsISupports *aSubject,
                                 const char *aTopic,
                                 const PRUnichar *someData)
 {
@@ -1415,6 +1414,8 @@ MemoryPressureObserver::Observe(nsISupports *aSubject,
         if (fontCache) {
             fontCache->FlushShapedWordCaches();
         }
+    } else {
+        NS_NOTREACHED("unexpected notification topic");
     }
     return NS_OK;
 }
@@ -1455,7 +1456,7 @@ gfxFontCache::gfxFontCache()
 {
     nsCOMPtr<nsIObserverService> obs = GetObserverService();
     if (obs) {
-        obs->AddObserver(new MemoryPressureObserver, "memory-pressure", false);
+        obs->AddObserver(new Observer, "memory-pressure", false);
     }
 
     mWordCacheExpirationTimer = do_CreateInstance("@mozilla.org/timer;1");

gfx/thebes/gfxFont.h

@@ -24,6 +24,7 @@
 #include "gfxPattern.h"
 #include "mozilla/HashFunctions.h"
 #include "nsIMemoryReporter.h"
+#include "nsIObserver.h"
 #include "gfxFontFeatures.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/gfx/Types.h"
@@ -400,6 +401,9 @@ public:
     gr_face* GetGrFace();
     virtual void ReleaseGrFace(gr_face* aFace);
 
+    // Release any SVG-glyphs document this font may have loaded.
+    void DisconnectSVG();
+
     // Called to notify that aFont is being destroyed. Needed when we're tracking
     // the fonts belonging to this font entry.
     void NotifyFontDestroyed(gfxFont* aFont);
@@ -951,6 +955,15 @@ protected:
         NS_DECL_NSIMEMORYREPORTER
     };
 
+    // Observer for notifications that the font cache cares about
+    class Observer MOZ_FINAL
+        : public nsIObserver
+    {
+    public:
+        NS_DECL_ISUPPORTS
+        NS_DECL_NSIOBSERVER
+    };
+
     void DestroyFont(gfxFont *aFont);
 
     static gfxFontCache *gGlobalCache;

gfx/thebes/gfxUserFontSet.cpp

@@ -810,6 +810,14 @@ gfxUserFontSet::UserFontCache::Entry::RemoveIfPrivate(Entry* aEntry,
     return aEntry->mPrivate ? PL_DHASH_REMOVE : PL_DHASH_NEXT;
 }
 
+PLDHashOperator
+gfxUserFontSet::UserFontCache::Entry::DisconnectSVG(Entry* aEntry,
+                                                    void* aUserData)
+{
+    aEntry->GetFontEntry()->DisconnectSVG();
+    return PL_DHASH_NEXT;
+}
+
 NS_IMETHODIMP
 gfxUserFontSet::UserFontCache::Flusher::Observe(nsISupports* aSubject,
                                                 const char* aTopic,
@@ -823,6 +831,8 @@ gfxUserFontSet::UserFontCache::Flusher::Observe(nsISupports* aSubject,
         sUserFonts->Clear();
     } else if (!strcmp(aTopic, "last-pb-context-exited")) {
         sUserFonts->EnumerateEntries(Entry::RemoveIfPrivate, nullptr);
+    } else if (!strcmp(aTopic, "xpcom-shutdown")) {
+        sUserFonts->EnumerateEntries(Entry::DisconnectSVG, nullptr);
     } else {
         NS_NOTREACHED("unexpected topic");
     }
@@ -874,6 +884,7 @@ gfxUserFontSet::UserFontCache::CacheFont(gfxFontEntry *aFontEntry)
             obs->AddObserver(flusher, NS_CACHESERVICE_EMPTYCACHE_TOPIC_ID,
                              false);
             obs->AddObserver(flusher, "last-pb-context-exited", false);
+            obs->AddObserver(flusher, "xpcom-shutdown", false);
         }
     }
 

gfx/thebes/gfxUserFontSet.h

@@ -346,6 +346,7 @@ public:
             gfxFontEntry* GetFontEntry() const { return mFontEntry; }
 
             static PLDHashOperator RemoveIfPrivate(Entry* aEntry, void* aUserData);
+            static PLDHashOperator DisconnectSVG(Entry* aEntry, void* aUserData);
 
         private:
             static uint32_t