Force instantiate <use> tree before updating SMIL animation

Source/core/svg/animation/SMILTimeContainer.cpp

 /*
  * Copyright (C) 2008 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.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 430 matching lines @@
     if (!earliestFireTime.isFinite())
         return;
 
     scheduleAnimationFrame(earliestFireTime);
 }
 
 SMILTime SMILTimeContainer::updateAnimations(SMILTime elapsed, bool seekToTime)
 {
     SMILTime earliestFireTime = SMILTime::unresolved();
 
+    // FIXME(crbug.com/478549): Force update use shadow trees before iterating m_scheduledAnimations, as shadow tree instantiation may modify m_scheduledAnimations.

[fs, 2015/04/23 10:48:59]

FIXME -> TODO

+    if (!m_scheduledAnimations.isEmpty())
+        document().updateRenderTreeIfNeeded();
+
 #if ENABLE(ASSERT)
     // This boolean will catch any attempts to schedule/unschedule scheduledAnimations during this critical section.
     // Similarly, any elements removed will unschedule themselves, so this will catch modification of animationsToApply.
     m_preventScheduledAnimationsChanges = true;
 #endif
 
     if (m_documentOrderIndexesDirty)
         updateDocumentOrderIndexes();
 
     WillBeHeapHashSet<ElementAttributePair> invalidKeys;
@@ skipping 76 matching lines @@
 }
 
 DEFINE_TRACE(SMILTimeContainer)
 {
 #if ENABLE(OILPAN)
     visitor->trace(m_scheduledAnimations);
 #endif
 }
 
 }