Run Mutation Observer and Custom Element callbacks consistently at microtask checkpoint

Source/bindings/v8/V8RecursionScope.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 13 matching lines @@
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "bindings/v8/V8RecursionScope.h"
 
-#include "core/dom/CustomElementRegistry.h"
-#include "core/dom/MutationObserver.h"
+#include "core/dom/Microtask.h"
 #include "modules/indexeddb/IDBPendingTransactionMonitor.h"
 
 namespace WebCore {
 
 void V8RecursionScope::didLeaveScriptContext()
 {
     // FIXME: Instrument any work that takes place when script exits to c++ (e.g. Mutation Observers).
 
     // Indexed DB requires that transactions are created with an internal |active| flag
     // set to true, but the flag becomes false when control returns to the event loop.
     IDBPendingTransactionMonitor::deactivateNewTransactions();
 
-    if (m_isDocumentContext) {
-        MutationObserver::deliverAllMutations();
-        CustomElementRegistry::deliverAllLifecycleCallbacks();
-    }
+    if (m_isDocumentContext)
+        Microtask::performCheckpoint();
 }
 
 } // namespace WebCore