Run Mutation Observer and Custom Element callbacks consistently at microtask checkpoint

Source/core/dom/CustomElementRegistry.cpp

Index: Source/core/dom/CustomElementRegistry.cpp
diff --git a/Source/core/dom/CustomElementRegistry.cpp b/Source/core/dom/CustomElementRegistry.cpp
index 779526a68bd306dfc7fa6bf506cbdc54e892d90e..b701868cc2309ef3c388e092d558ac327adc959a 100644
--- a/Source/core/dom/CustomElementRegistry.cpp
+++ b/Source/core/dom/CustomElementRegistry.cpp
@@ -325,4 +325,21 @@ void CustomElementRegistry::deliverAllLifecycleCallbacks()
     }
 }
 
+bool CustomElementRegistry::hasQueuedLifecycleCallbacks()
+{
+    return !activeCustomElementRegistries().isEmpty();
+}
+
+void CustomElementRegistry::abandonAllQueuedLifecycleCallbacks()
+{
+    for (InstanceSet::iterator it = activeCustomElementRegistries().begin(); it != activeCustomElementRegistries().end(); ++it)
+        (*it)->abandonQueuedLifecycleCallbacks();
+    activeCustomElementRegistries().clear();
+}
+
+void CustomElementRegistry::abandonQueuedLifecycleCallbacks()
+{
+    m_invocations.clear();
+}
+
 }