Bug 968031: Remove threadsafe refcounting from ContentParent and add it to the cycle collector graph. r=bent,mccr8

dom/ipc/ContentParent.cpp

@@ -778,11 +778,6 @@ ContentParent::Init()
         }
     }
     Preferences::AddStrongObserver(this, "");
-    nsCOMPtr<nsIThreadInternal>
-            threadInt(do_QueryInterface(NS_GetCurrentThread()));
-    if (threadInt) {
-        threadInt->AddObserver(this);
-    }
     if (obs) {
         obs->NotifyObservers(static_cast<nsIObserver*>(this), "ipc:content-created", nullptr);
     }
@@ -1137,8 +1132,7 @@ ContentParent::ActorDestroy(ActorDestroyReason why)
                           CHILD_PROCESS_SHUTDOWN_MESSAGE, false,
                           nullptr, nullptr, nullptr, nullptr);
     }
-    nsCOMPtr<nsIThreadObserver>
-        kungFuDeathGrip(static_cast<nsIThreadObserver*>(this));
+    nsRefPtr<ContentParent> kungFuDeathGrip(this);
     nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
     if (obs) {
         size_t length = ArrayLength(sObserverTopics);
@@ -1171,11 +1165,6 @@ ContentParent::ActorDestroy(ActorDestroyReason why)
 
     mConsoleService = nullptr;
 
-    nsCOMPtr<nsIThreadInternal>
-        threadInt(do_QueryInterface(NS_GetCurrentThread()));
-    if (threadInt)
-        threadInt->RemoveObserver(this);
-
     MarkAsDead();
 
     if (obs) {
@@ -1961,10 +1950,18 @@ ContentParent::RecvAddNewProcess(const uint32_t& aPid,
 #endif
 }
 
-NS_IMPL_ISUPPORTS3(ContentParent,
-                   nsIObserver,
-                   nsIThreadObserver,
-                   nsIDOMGeoPositionCallback)
+// We want ContentParent to show up in CC logs for debugging purposes, but we
+// don't actually cycle collect it.
+NS_IMPL_CYCLE_COLLECTION_0(ContentParent)
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(ContentParent)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(ContentParent)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ContentParent)
+  NS_INTERFACE_MAP_ENTRY(nsIObserver)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMGeoPositionCallback)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIObserver)
+NS_INTERFACE_MAP_END
 
 NS_IMETHODIMP
 ContentParent::Observe(nsISupports* aSubject,
@@ -2857,32 +2854,6 @@ ContentParent::RecvLoadURIExternal(const URIParams& uri)
     return true;
 }
 
-/* void onDispatchedEvent (in nsIThreadInternal thread); */
-NS_IMETHODIMP
-ContentParent::OnDispatchedEvent(nsIThreadInternal *thread)
-{
-   NS_NOTREACHED("OnDispatchedEvent unimplemented");
-   return NS_ERROR_NOT_IMPLEMENTED;
-}
-
-/* void onProcessNextEvent (in nsIThreadInternal thread, in boolean mayWait, in unsigned long recursionDepth); */
-NS_IMETHODIMP
-ContentParent::OnProcessNextEvent(nsIThreadInternal *thread,
-                                  bool mayWait,
-                                  uint32_t recursionDepth)
-{
-    return NS_OK;
-}
-
-/* void afterProcessNextEvent (in nsIThreadInternal thread, in unsigned long recursionDepth); */
-NS_IMETHODIMP
-ContentParent::AfterProcessNextEvent(nsIThreadInternal *thread,
-                                     uint32_t recursionDepth,
-                                     bool eventWasProcessed)
-{
-    return NS_OK;
-}
-
 bool
 ContentParent::RecvShowAlertNotification(const nsString& aImageUrl, const nsString& aTitle,
                                          const nsString& aText, const bool& aTextClickable,

dom/ipc/ContentParent.h

@@ -60,7 +60,6 @@ class TabContext;
 
 class ContentParent : public PContentParent
                     , public nsIObserver
-                    , public nsIThreadObserver
                     , public nsIDOMGeoPositionCallback
                     , public mozilla::dom::ipc::MessageManagerCallback
                     , public mozilla::LinkedListElement<ContentParent>
@@ -112,9 +111,10 @@ public:
     static void GetAll(nsTArray<ContentParent*>& aArray);
     static void GetAllEvenIfDead(nsTArray<ContentParent*>& aArray);
 
-    NS_DECL_THREADSAFE_ISUPPORTS
+    NS_DECL_CYCLE_COLLECTION_CLASS_AMBIGUOUS(ContentParent, nsIObserver)
+
+    NS_DECL_CYCLE_COLLECTING_ISUPPORTS
     NS_DECL_NSIOBSERVER
-    NS_DECL_NSITHREADOBSERVER
     NS_DECL_NSIDOMGEOPOSITIONCALLBACK
 
     /**

xpcom/glue/nsCycleCollectionParticipant.h

@@ -710,12 +710,19 @@ static NS_CYCLE_COLLECTION_INNERCLASS NS_CYCLE_COLLECTION_INNERNAME;
     tmp->_unroot_function();                                                   \
   }
 
-// NS_IMPL_CYCLE_COLLECTION_0 is not defined because most of the time it doesn't
-// make sense to add something to the CC that doesn't traverse to anything.
-
 #define NS_IMPL_CYCLE_COLLECTION_CLASS(_class) \
  _class::NS_CYCLE_COLLECTION_INNERCLASS _class::NS_CYCLE_COLLECTION_INNERNAME;
 
+// NB: This is not something you usually want to use.  It is here to allow
+// adding things to the CC graph to help debugging via CC logs, but it does not
+// traverse or unlink anything, so it is useless for anything else.
+#define NS_IMPL_CYCLE_COLLECTION_0(_class)                                     \
+ NS_IMPL_CYCLE_COLLECTION_CLASS(_class)                                        \
+ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(_class)                                 \
+ NS_IMPL_CYCLE_COLLECTION_UNLINK_END                                           \
+ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(_class)                               \
+ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
 #define NS_IMPL_CYCLE_COLLECTION_1(_class, _f)                                 \
  NS_IMPL_CYCLE_COLLECTION_CLASS(_class)                                        \
  NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(_class)                                 \