Make dispatchIfAlive ensure the life of its queue.

Source/core/dom/custom/CustomElementMicrotaskRunQueue.cpp

Index: Source/core/dom/custom/CustomElementMicrotaskRunQueue.cpp
diff --git a/Source/core/dom/custom/CustomElementMicrotaskRunQueue.cpp b/Source/core/dom/custom/CustomElementMicrotaskRunQueue.cpp
index a7e6d2642870572efa42492fc3a82f71d1dff259..341b5b39937c358a8e550f79ec643f6a6d3c51c0 100644
--- a/Source/core/dom/custom/CustomElementMicrotaskRunQueue.cpp
+++ b/Source/core/dom/custom/CustomElementMicrotaskRunQueue.cpp
@@ -40,8 +40,10 @@ void CustomElementMicrotaskRunQueue::enqueue(HTMLImportLoader* parentLoader, Pas
 
 void CustomElementMicrotaskRunQueue::dispatchIfAlive(WeakPtr<CustomElementMicrotaskRunQueue> self)
 {
-    if (self.get())
+    if (self.get()) {
+        RefPtrWillBeRawPtr<CustomElementMicrotaskRunQueue> protect(self.get());
         self->dispatch();
+    }
 }
 
 void CustomElementMicrotaskRunQueue::requestDispatchIfNeeded()