Create & use microtask work queue

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index aae58dd8cb95fb376936800d57d8fddd5915a598..b9bc63bd393d37fdf10598973bca72ab7f610d77 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -74,6 +74,7 @@
 #include "core/dom/ExceptionCode.h"
 #include "core/dom/ExecutionContextTask.h"
 #include "core/dom/MainThreadTaskRunner.h"
+#include "core/dom/MutationObserver.h"
 #include "core/dom/NamedFlowCollection.h"
 #include "core/dom/NodeChildRemovalTracker.h"
 #include "core/dom/NodeFilter.h"
@@ -4808,6 +4809,8 @@ void Document::tasksWereResumed()
         m_parser->resumeScheduledTasks();
     if (m_scriptedAnimationController)
         m_scriptedAnimationController->resume();
+
+    MutationObserver::resumeSuspendedObservers();
 }
 
 // FIXME: suspendScheduledTasks(), resumeScheduledTasks(), tasksNeedSuspension()