Bug 1195180 part 2 - Make DocumentTimeline inherit from nsARefreshObserver; r=heycam

dom/animation/DocumentTimeline.cpp

@@ -91,6 +91,11 @@ DocumentTimeline::ToTimelineTime(const TimeStamp& aTimeStamp) const
   return result;
 }
 
+void
+DocumentTimeline::WillRefresh(mozilla::TimeStamp aTime)
+{
+}
+
 TimeStamp
 DocumentTimeline::ToTimeStamp(const TimeDuration& aTimeDuration) const
 {

dom/animation/DocumentTimeline.h

@@ -17,7 +17,9 @@ struct JSContext;
 namespace mozilla {
 namespace dom {
 
-class DocumentTimeline final : public AnimationTimeline
+class DocumentTimeline final
+  : public AnimationTimeline
+  , public nsARefreshObserver
 {
 public:
   explicit DocumentTimeline(nsIDocument* aDocument)
@@ -50,6 +52,9 @@ public:
                                                                      override;
   TimeStamp ToTimeStamp(const TimeDuration& aTimelineTime) const override;
 
+  // nsARefreshObserver methods
+  void WillRefresh(TimeStamp aTime) override;
+
 protected:
   TimeStamp GetCurrentTimeStamp() const;
   nsRefreshDriver* GetRefreshDriver() const;