Bug 609814: Unregister SVGDocumentWrapper as XPCOM shutdown observer when we're done with it. r=roc a=blocking-final

modules/libpr0n/src/SVGDocumentWrapper.cpp

@@ -68,13 +68,15 @@ namespace imagelib {
 
 nsIAtom* SVGDocumentWrapper::kSVGAtom = nsnull; // lazily initialized
 
-NS_IMPL_ISUPPORTS3(SVGDocumentWrapper,
+NS_IMPL_ISUPPORTS4(SVGDocumentWrapper,
                    nsIStreamListener,
                    nsIRequestObserver,
-                   nsIObserver)
+                   nsIObserver,
+                   nsISupportsWeakReference)
 
 SVGDocumentWrapper::SVGDocumentWrapper()
- : mIgnoreInvalidation(PR_FALSE)
+  : mIgnoreInvalidation(PR_FALSE),
+    mRegisteredForXPCOMShutdown(PR_FALSE)
 {
   // Lazy-initialize our "svg" atom.  (It'd be nicer to just use nsGkAtoms::svg
   // directly, but we can't access it from here in non-libxul builds.)
@@ -87,6 +89,9 @@ SVGDocumentWrapper::SVGDocumentWrapper()
 SVGDocumentWrapper::~SVGDocumentWrapper()
 {
   DestroyViewer();
+  if (mRegisteredForXPCOMShutdown) {
+    UnregisterForXPCOMShutdown();
+  }
 }
 
 void
@@ -376,6 +381,8 @@ SVGDocumentWrapper::SetupViewer(nsIRequest* aRequest,
 void
 SVGDocumentWrapper::RegisterForXPCOMShutdown()
 {
+  NS_ABORT_IF_FALSE(!mRegisteredForXPCOMShutdown,
+                    "re-registering for XPCOM shutdown");
   // Listen for xpcom-shutdown so that we can drop references to our
   // helper-document at that point. (Otherwise, we won't get cleaned up
   // until imgLoader::Shutdown, which can happen after the JAR service
@@ -384,8 +391,26 @@ SVGDocumentWrapper::RegisterForXPCOMShutdown()
   nsCOMPtr<nsIObserverService> obsSvc = do_GetService(OBSERVER_SVC_CID, &rv);
   if (NS_FAILED(rv) ||
       NS_FAILED(obsSvc->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID,
-                                    PR_FALSE))) {
+                                    PR_TRUE))) {
     NS_WARNING("Failed to register as observer of XPCOM shutdown");
+  } else {
+    mRegisteredForXPCOMShutdown = PR_TRUE;
+  }
+}
+
+void
+SVGDocumentWrapper::UnregisterForXPCOMShutdown()
+{
+  NS_ABORT_IF_FALSE(mRegisteredForXPCOMShutdown,
+                    "unregistering for XPCOM shutdown w/out being registered");
+
+  nsresult rv;
+  nsCOMPtr<nsIObserverService> obsSvc = do_GetService(OBSERVER_SVC_CID, &rv);
+  if (NS_FAILED(rv) ||
+      NS_FAILED(obsSvc->RemoveObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID))) {
+    NS_WARNING("Failed to unregister as observer of XPCOM shutdown");
+  } else {
+    mRegisteredForXPCOMShutdown = PR_FALSE;
   }
 }
 

modules/libpr0n/src/SVGDocumentWrapper.h

@@ -45,6 +45,7 @@
 #include "nsIStreamListener.h"
 #include "nsIObserver.h"
 #include "nsIDocumentViewer.h"
+#include "nsWeakReference.h"
 
 class nsIAtom;
 class nsIPresShell;
@@ -63,7 +64,8 @@ namespace mozilla {
 namespace imagelib {
 
 class SVGDocumentWrapper : public nsIStreamListener,
-                           public nsIObserver
+                           public nsIObserver,
+                           nsSupportsWeakReference
 {
 public:
   SVGDocumentWrapper();
@@ -165,6 +167,7 @@ private:
                        nsILoadGroup** aLoadGroup);
   void     DestroyViewer();
   void     RegisterForXPCOMShutdown();
+  void     UnregisterForXPCOMShutdown();
 
   void     FlushLayout();
 
@@ -172,6 +175,7 @@ private:
   nsCOMPtr<nsILoadGroup>      mLoadGroup;
   nsCOMPtr<nsIStreamListener> mListener;
   PRPackedBool                mIgnoreInvalidation;
+  PRPackedBool                mRegisteredForXPCOMShutdown;
 
   // Lazily-initialized pointer to nsGkAtoms::svg, to make life easier in
   // non-libxul builds, which don't let us reference nsGkAtoms from imagelib.