Use intersection observer to control frame throttling

third_party/WebKit/Source/core/frame/FrameView.h

Index: third_party/WebKit/Source/core/frame/FrameView.h
diff --git a/third_party/WebKit/Source/core/frame/FrameView.h b/third_party/WebKit/Source/core/frame/FrameView.h
index b07546a6bf4dd190c9e3cf0bfa2ad4a15e8d81e7..d13d6a2ef407e0dacbb2c8d410ac8f21e0c2b454 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.h
+++ b/third_party/WebKit/Source/core/frame/FrameView.h
@@ -63,6 +63,7 @@ class ComputedStyle;
 class DocumentLifecycle;
 class Cursor;
 class Element;
+class ElementVisibilityObserver;
 class FloatSize;
 class JSONArray;
 class JSONObject;
@@ -675,10 +676,11 @@ class CORE_EXPORT FrameView final
   // scheduling visual updates.
   bool canThrottleRendering() const;
   bool isHiddenForThrottling() const { return m_hiddenForThrottling; }
+  void setupRenderThrottling();
 
   // For testing, run pending intersection observer notifications for this
   // frame.
-  void notifyRenderThrottlingObserversForTesting();
+  void updateRenderThrottlingStatusForTesting();
 
   // Paint properties for SPv2 Only.
   void setPreTranslation(
@@ -919,9 +921,7 @@ class CORE_EXPORT FrameView final
   void setNeedsUpdateViewportIntersection();
   void updateViewportIntersectionsForSubtree(
       DocumentLifecycle::LifecycleState targetState);
-  void updateViewportIntersectionIfNeeded();
-  void notifyRenderThrottlingObservers();
-  void updateThrottlingStatus();
+  void updateRenderThrottlingStatus(bool hidden, bool subtreeThrottled);
   void notifyResizeObservers();
 
   // PaintInvalidationCapableScrollableArea
@@ -963,8 +963,6 @@ class CORE_EXPORT FrameView final
   unsigned m_nestedLayoutCount;
   Timer<FrameView> m_postLayoutTasksTimer;
   Timer<FrameView> m_updateWidgetsTimer;
-  std::unique_ptr<CancellableTaskFactory>
-      m_renderThrottlingObserverNotificationFactory;
 
   bool m_firstLayout;
   bool m_isTransparent;
@@ -1044,16 +1042,10 @@ class CORE_EXPORT FrameView final
   // main frame.
   Member<RootFrameViewport> m_viewportScrollableArea;
 
-  // This frame's bounds in the root frame's content coordinates, clipped
-  // recursively through every ancestor view.
-  IntRect m_viewportIntersection;
-  bool m_viewportIntersectionValid;
-
   // The following members control rendering pipeline throttling for this
   // frame. They are only updated in response to intersection observer
   // notifications, i.e., not in the middle of the lifecycle.
   bool m_hiddenForThrottling;
-  bool m_crossOriginForThrottling;
   bool m_subtreeThrottled;
 
   // Paint properties for SPv2 Only.
@@ -1090,6 +1082,8 @@ class CORE_EXPORT FrameView final
   bool m_suppressAdjustViewSize;
   bool m_allowsLayoutInvalidationAfterLayoutClean;
 
+  Member<ElementVisibilityObserver> m_visibilityObserver;
+
   // For testing.
   struct ObjectPaintInvalidation {
     String name;