--- a/js/xpconnect/src/XPCJSRuntime.cpp
+++ b/js/xpconnect/src/XPCJSRuntime.cpp
@@ -106,19 +106,16 @@ xpc::ShouldDiscardSystemSource() { retur
 
 #ifdef DEBUG
 static mozilla::Atomic<bool> sExtraWarningsForSystemJS(false);
 bool xpc::ExtraWarningsForSystemJS() { return sExtraWarningsForSystemJS; }
 #else
 bool xpc::ExtraWarningsForSystemJS() { return false; }
 #endif
 
-static void * const UNMARK_ONLY = nullptr;
-static void * const UNMARK_AND_SWEEP = (void*)1;
-
 // *Some* NativeSets are referenced from mClassInfo2NativeSetMap.
 // *All* NativeSets are referenced from mNativeSetMap.
 // So, in mClassInfo2NativeSetMap we just clear references to the unmarked.
 // In mNativeSetMap we clear the references to the unmarked *and* delete them.
 
 bool
 XPCJSRuntime::CustomContextCallback(JSContext* cx, unsigned operation)
 {
@@ -806,71 +803,62 @@ XPCJSRuntime::FinalizeCallback(JSFreeOp*
             // marked, so it is not safe to sweep them. We still need to unmark
             // them, since the ones pointed to by WrappedNativeProtos in a
             // compartment being collected will be marked.
             //
             // Ideally, if NativeInterfaces from different compartments were
             // kept separate, we could sweep only the ones belonging to
             // compartments being collected. Currently, though, NativeInterfaces
             // are shared between compartments. This ought to be fixed.
-            void* sweepArg = isCompartmentGC ? UNMARK_ONLY : UNMARK_AND_SWEEP;
+            bool doSweep = !isCompartmentGC;
 
             // We don't want to sweep the JSClasses at shutdown time.
             // At this point there may be JSObjects using them that have
             // been removed from the other maps.
             if (!nsXPConnect::XPConnect()->IsShuttingDown()) {
                 for (auto i = self->mNativeScriptableSharedMap->RemovingIter(); !i.Done(); i.Next()) {
                     auto entry = static_cast<XPCNativeScriptableSharedMap::Entry*>(i.Get());
                     XPCNativeScriptableShared* shared = entry->key;
                     if (shared->IsMarked()) {
                         shared->Unmark();
-                        continue;
+                    } else if (doSweep) {
+                        delete shared;
+                        i.Remove();
                     }
-                    if (sweepArg == UNMARK_ONLY)
-                        continue;
-
-                    delete shared;
-                    i.Remove();
                 }
             }
 
             if (!isCompartmentGC) {
                 for (auto i = self->mClassInfo2NativeSetMap->RemovingIter(); !i.Done(); i.Next()) {
                     auto entry = static_cast<ClassInfo2NativeSetMap::Entry*>(i.Get());
                     if (!entry->value->IsMarked())
                         i.Remove();
                 }
             }
 
             for (auto i = self->mNativeSetMap->RemovingIter(); !i.Done(); i.Next()) {
                 auto entry = static_cast<NativeSetMap::Entry*>(i.Get());
                 XPCNativeSet* set = entry->key_value;
                 if (set->IsMarked()) {
                     set->Unmark();
-                    continue;
+                } else if (doSweep) {
+                    XPCNativeSet::DestroyInstance(set);
+                    i.Remove();
                 }
-                if (sweepArg == UNMARK_ONLY)
-                    continue;
-
-                XPCNativeSet::DestroyInstance(set);
-                i.Remove();
             }
 
             for (auto i = self->mIID2NativeInterfaceMap->RemovingIter(); !i.Done(); i.Next()) {
                 auto entry = static_cast<IID2NativeInterfaceMap::Entry*>(i.Get());
                 XPCNativeInterface* iface = entry->value;
                 if (iface->IsMarked()) {
                     iface->Unmark();
-                    continue;
+                } else if (doSweep) {
+                    XPCNativeInterface::DestroyInstance(iface);
+                    i.Remove();
                 }
-                if (sweepArg == UNMARK_ONLY)
-                    continue;
-
-                XPCNativeInterface::DestroyInstance(iface);
-                i.Remove();
             }
 
 #ifdef DEBUG
             XPCWrappedNativeScope::ASSERT_NoInterfaceSetsAreMarked();
 #endif
 
             // Now we are going to recycle any unused WrappedNativeTearoffs.
             // We do this by iterating all the live callcontexts