Ensure serviceOnNextFrame isn't put off indefinitely.

Source/core/animation/AnimationTimeline.h

 /*
  * Copyright (C) 2013 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 120 matching lines @@
     OwnPtrWillBeMember<PlatformTiming> m_timing;
     double m_lastCurrentTimeInternal;
 
     OwnPtr<WebCompositorAnimationTimeline> m_compositorTimeline;
 
     class AnimationTimelineTiming final : public PlatformTiming {
     public:
         AnimationTimelineTiming(AnimationTimeline* timeline)
             : m_timeline(timeline)
             , m_timer(this, &AnimationTimelineTiming::timerFired)
+            , m_currentScheduledTime(std::numeric_limits<double>::infinity())
         {
             ASSERT(m_timeline);
         }
 
         void wakeAfter(double duration) override;
         void cancelWake() override;
         void serviceOnNextFrame() override;
 
         void timerFired(Timer<AnimationTimelineTiming>*) { m_timeline->wake(); }
 
         DECLARE_VIRTUAL_TRACE();
 
     private:
         RawPtrWillBeMember<AnimationTimeline> m_timeline;
         Timer<AnimationTimelineTiming> m_timer;
+        double m_currentScheduledTime;
     };
 
     friend class AnimationAnimationTimelineTest;
 };
 
 } // namespace blink
 
 #endif