Use intersection observer to control frame throttling

third_party/WebKit/Source/core/dom/IntersectionObserverController.h

Index: third_party/WebKit/Source/core/dom/IntersectionObserverController.h
diff --git a/third_party/WebKit/Source/core/dom/IntersectionObserverController.h b/third_party/WebKit/Source/core/dom/IntersectionObserverController.h
index f577121caafb3b5d44bcb186072a5fd5d7dc89ef..52fc2869eb067a3b9a6dfad850743a14525e0f5a 100644
--- a/third_party/WebKit/Source/core/dom/IntersectionObserverController.h
+++ b/third_party/WebKit/Source/core/dom/IntersectionObserverController.h
@@ -16,6 +16,7 @@
 
 namespace blink {
 
+class CancellableTaskFactory;
 class Document;
 
 class IntersectionObserverController : public IdleRequestCallback, public ActiveDOMObject {
@@ -39,13 +40,19 @@ private:
     explicit IntersectionObserverController(Document*);
 
 private:
+    void deliverLowLatencyNotifications();
+
     // IntersectionObservers for which this is the tracking document.
     HeapHashSet<WeakMember<IntersectionObserver>> m_trackedIntersectionObservers;
     // IntersectionObservers for which this is the execution context of the callback.
     HeapHashSet<Member<IntersectionObserver>> m_pendingIntersectionObservers;
+    HeapHashSet<Member<IntersectionObserver>> m_pendingLowLatencyIntersectionObservers;
+
+    std::unique_ptr<CancellableTaskFactory> m_lowLatencyNotificationTask;
 
     int m_callbackID;
     bool m_callbackFiredWhileSuspended;
+    bool m_lowLatencyCallbackFiredWhileSuspended;
 };
 
 } // namespace blink