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 d8f183533b304cbc72c827789d3e7ae11255013c..0c8655aec0ed8c874c07a03dd98096892d075d74 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.h
+++ b/third_party/WebKit/Source/core/frame/FrameView.h
@@ -28,6 +28,7 @@
 
 #include "core/CoreExport.h"
 #include "core/dom/DocumentLifecycle.h"
+#include "core/dom/IntersectionObserverCallback.h"
 #include "core/frame/FrameViewAutoSizeInfo.h"
 #include "core/frame/LayoutSubtreeRootList.h"
 #include "core/frame/RootFrameViewport.h"
@@ -670,10 +671,11 @@ 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(
@@ -773,6 +775,23 @@ class CORE_EXPORT FrameView final
   void invalidateTreeIfNeeded(const PaintInvalidationState&);
 
  private:
+  class IntersectionObserverCallback
+      : public blink::IntersectionObserverCallback {
+   public:
+    IntersectionObserverCallback(FrameView*, ExecutionContext*);
+
+    // IntersectionObserverCallback implementation:
+    void handleEvent(const HeapVector<Member<IntersectionObserverEntry>>&,
+                     IntersectionObserver&) override;
+    ExecutionContext* getExecutionContext() const override;
+
+    DECLARE_TRACE();
+
+   private:
+    WeakMember<FrameView> m_frameView;
+    WeakMember<ExecutionContext> m_context;
+  };
+
   explicit FrameView(LocalFrame*);
 
   void updateScrollOffset(const ScrollOffset&, ScrollType) override;
@@ -897,9 +916,7 @@ 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
@@ -941,8 +958,6 @@ 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;
@@ -1023,16 +1038,10 @@ 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.
@@ -1063,6 +1072,8 @@ class CORE_EXPORT FrameView final
   bool m_suppressAdjustViewSize;
   bool m_allowsLayoutInvalidationAfterLayoutClean;
 
+  Member<IntersectionObserver> m_intersectionObserver;
+
   // For testing.
   struct ObjectPaintInvalidation {
     String name;