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 55f071cafc334489d06d45c50113a5303dd18096..570c3caa3603b464aa6f563de83d28a6b5de65da 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.h
+++ b/third_party/WebKit/Source/core/frame/FrameView.h
@@ -27,6 +27,7 @@
 
 #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"
@@ -591,9 +592,10 @@ public:
     // 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(PassRefPtr<TransformPaintPropertyNode> preTranslation) { m_preTranslation = preTranslation; }
@@ -668,6 +670,20 @@ protected:
     void invalidateTreeIfNeeded(const PaintInvalidationState&);
 
 private:
+    class IntersectionObserverCallback : public blink::IntersectionObserverCallback {
+    public:
+        IntersectionObserverCallback(FrameView*);
+
+        // IntersectionObserverCallback implementation:
+        void handleEvent(const HeapVector<Member<IntersectionObserverEntry>>&, IntersectionObserver&) override;
+        ExecutionContext* getExecutionContext() const override;
+
+        DECLARE_TRACE();
+
+    private:
+        Member<FrameView> m_frameView;

[szager1, 2016/08/30 23:57:12]

I think this should be WeakMember, to avoid a reference cycle:

FrameView->IntersectionObserver->IntersectionObserverCallback->FrameView.

[Sami, 2016/08/31 11:08:56]

I guess I was thinking that with Oilpan in-heap reference cycles aren't an issue
anymore, but maybe a WeakMember is still more appropriate? Done.

+    };
+
     explicit FrameView(LocalFrame*);
 
     void setScrollOffset(const DoublePoint&, ScrollType) override;
@@ -778,9 +794,7 @@ private:
 
     void setNeedsUpdateViewportIntersection();
     void updateViewportIntersectionsForSubtree(DocumentLifecycle::LifecycleState targetState);
-    void updateViewportIntersectionIfNeeded();
-    void notifyRenderThrottlingObservers();
-    void updateThrottlingStatus();
+    void updateRenderThrottlingStatus(bool hidden, bool subtreeThrottled);
     void notifyResizeObservers();
 
     // PaintInvalidationCapableScrollableArea
@@ -819,7 +833,6 @@ private:
     unsigned m_nestedLayoutCount;
     Timer<FrameView> m_postLayoutTasksTimer;
     Timer<FrameView> m_updateWidgetsTimer;
-    std::unique_ptr<CancellableTaskFactory> m_renderThrottlingObserverNotificationFactory;
 
     bool m_firstLayout;
     bool m_isTransparent;
@@ -901,16 +914,10 @@ private:
     // 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.
@@ -939,6 +946,8 @@ private:
     bool m_suppressAdjustViewSize;
     bool m_allowsLayoutInvalidationAfterLayoutClean;
 
+    Member<IntersectionObserver> m_intersectionObserver;
+
     // For testing.
     struct ObjectPaintInvalidation {
         String name;