ResizeObserver pt5: size change notification

third_party/WebKit/Source/core/observer/ResizeObserverController.h

Index: third_party/WebKit/Source/core/observer/ResizeObserverController.h
diff --git a/third_party/WebKit/Source/core/observer/ResizeObserverController.h b/third_party/WebKit/Source/core/observer/ResizeObserverController.h
index e84ef621ee747c31a93d6245c504355aaccd05e0..49265289100c0c142bd2fa88d7d7cf2deb1e378d 100644
--- a/third_party/WebKit/Source/core/observer/ResizeObserverController.h
+++ b/third_party/WebKit/Source/core/observer/ResizeObserverController.h
@@ -13,17 +13,36 @@ class ResizeObserver;
 
 // ResizeObserverController keeps track of all ResizeObservers
 // in a single Document.
+//
+// The observation API is used to integrate ResizeObserver
+// and the event loop. It delivers notification in a loop.
+// In each iteration, only notifications deeper than the
+// shallowest notification from previous iteration are delivered.
 class ResizeObserverController final : public GarbageCollected<ResizeObserverController> {
 public:
+    static const size_t kDepthBottom = 4096;
+
     ResizeObserverController();
 
     void addObserver(ResizeObserver&);
 
+    // observation API
+    // Returns depth of shallowest observed node, kDepthLimit if none.
+    size_t gatherObservations(size_t deeperThan);
+    // Returns true if gatherObservations has skipped observations
+    // because they were too shallow.
+    bool skippedObservations();
+    void deliverObservations();
+    void clearObservations();
+    void observerChanged()  { m_observersChanged = true; }
+
     DECLARE_TRACE();
 
 private:
     // Active observers
     HeapHashSet<WeakMember<ResizeObserver>> m_observers;
+    // True if any observers were changed since last notification.
+    bool m_observersChanged;
 };
 
 } // namespace blink