Bug 716661 - Convert observers in nsDownloadManager to weak observers. r=mak

Make nsDownloadManager inherit from nsSupportsWeakReference, expose
the new interface, and change the last argument of the addObserver
calls to true to signify that we are adding a weak observer.

toolkit/components/downloads/nsDownloadManager.cpp

@@ -111,11 +111,12 @@ static const PRInt64 gUpdateInterval = 400 * PR_USEC_PER_MSEC;
 ////////////////////////////////////////////////////////////////////////////////
 //// nsDownloadManager
 
-NS_IMPL_ISUPPORTS3(
+NS_IMPL_ISUPPORTS4(
   nsDownloadManager
 , nsIDownloadManager
 , nsINavHistoryObserver
 , nsIObserver
+, nsISupportsWeakReference
 )
 
 nsDownloadManager *nsDownloadManager::gDownloadManagerService = nsnull;
@@ -886,23 +887,19 @@ nsDownloadManager::Init()
   // completely initialized), but the observerservice would still keep a reference
   // to us and notify us about shutdown, which may cause crashes.
   // failure to add an observer is not critical
-  //
-  // These observers will be cleaned up automatically at app shutdown.  We do
-  // not bother explicitly breaking the observers because we are a singleton
-  // that lives for the duration of the app.
-  (void)mObserverService->AddObserver(this, "quit-application", false);
-  (void)mObserverService->AddObserver(this, "quit-application-requested", false);
-  (void)mObserverService->AddObserver(this, "offline-requested", false);
-  (void)mObserverService->AddObserver(this, "sleep_notification", false);
-  (void)mObserverService->AddObserver(this, "wake_notification", false);
-  (void)mObserverService->AddObserver(this, "profile-before-change", false);
-  (void)mObserverService->AddObserver(this, NS_IOSERVICE_GOING_OFFLINE_TOPIC, false);
-  (void)mObserverService->AddObserver(this, NS_IOSERVICE_OFFLINE_STATUS_TOPIC, false);
-  (void)mObserverService->AddObserver(this, NS_PRIVATE_BROWSING_REQUEST_TOPIC, false);
-  (void)mObserverService->AddObserver(this, NS_PRIVATE_BROWSING_SWITCH_TOPIC, false);
+  (void)mObserverService->AddObserver(this, "quit-application", true);
+  (void)mObserverService->AddObserver(this, "quit-application-requested", true);
+  (void)mObserverService->AddObserver(this, "offline-requested", true);
+  (void)mObserverService->AddObserver(this, "sleep_notification", true);
+  (void)mObserverService->AddObserver(this, "wake_notification", true);
+  (void)mObserverService->AddObserver(this, "profile-before-change", true);
+  (void)mObserverService->AddObserver(this, NS_IOSERVICE_GOING_OFFLINE_TOPIC, true);
+  (void)mObserverService->AddObserver(this, NS_IOSERVICE_OFFLINE_STATUS_TOPIC, true);
+  (void)mObserverService->AddObserver(this, NS_PRIVATE_BROWSING_REQUEST_TOPIC, true);
+  (void)mObserverService->AddObserver(this, NS_PRIVATE_BROWSING_SWITCH_TOPIC, true);
 
   if (history)
-    (void)history->AddObserver(this, false);
+    (void)history->AddObserver(this, true);
 
   return NS_OK;
 }

toolkit/components/downloads/nsDownloadManager.h

@@ -58,6 +58,7 @@
 #include "nsIObserverService.h"
 #include "nsIStringBundle.h"
 #include "nsISupportsPrimitives.h"
+#include "nsWeakReference.h"
 #include "nsITimer.h"
 #include "nsString.h"
 
@@ -76,7 +77,8 @@ class nsDownload;
 
 class nsDownloadManager : public nsIDownloadManager,
                           public nsINavHistoryObserver,
-                          public nsIObserver
+                          public nsIObserver,
+                          public nsSupportsWeakReference
 {
 public:
   NS_DECL_ISUPPORTS