If a compositing update is declared as needed, scheduleAnimation should be triggered.

Source/core/testing/Internals.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013 Apple 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 2305 matching lines @@
         return;
     }
 
     document->updateLayout();
 
     RenderView* view = document->renderView();
     if (view->compositor())
         view->compositor()->updateCompositingLayers();
 }
 
+bool Internals::isCompositorFramePending(Document* document, ExceptionState& exceptionState)
+{
+    if (!document || !document->renderView()) {
+        exceptionState.throwDOMException(InvalidAccessError, document ? "The document's render view cannot be retrieved." : "The document provided is invalid.");
+        return false;
+    }
+
+    return document->page()->chrome().client().isCompositorFramePending();
+}
+
 void Internals::setZoomFactor(float factor)
 {
     frame()->setPageZoomFactor(factor);
 }
 
 void Internals::setShouldRevealPassword(Element* element, bool reveal, ExceptionState& exceptionState)
 {
     if (!element || !element->hasTagName(inputTag)) {
         exceptionState.throwUninformativeAndGenericDOMException(InvalidAccessError);
         return;
@@ skipping 29 matching lines @@
 };
 
 } // namespace
 
 ScriptPromise Internals::addOneToPromise(ExecutionContext* context, ScriptPromise promise)
 {
     return promise.then(AddOneFunction::create(context));
 }
 
 }