Add root margin support for IntersectionObserver.

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef IntersectionObserver_h
 #define IntersectionObserver_h
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/dom/Element.h"
 #include "core/dom/IntersectionObservation.h"
@@ skipping 16 matching lines @@
     static IntersectionObserver* create(const IntersectionObserverInit&, IntersectionObserverCallback&, ExceptionState&);
     static void resumeSuspendedObservers();
 
     // API methods
     void observe(Element*, ExceptionState&);
     void unobserve(Element*, ExceptionState&);
     HeapVector<Member<IntersectionObserverEntry>> takeRecords();
 
     Element* root() { return m_root.get(); }
     LayoutObject* rootLayoutObject();
+    bool hasPercentMargin() const;
+    const Length& topMargin() const { return m_topMargin; }
+    const Length& rightMargin() const { return m_rightMargin; }
+    const Length& bottomMargin() const { return m_bottomMargin; }
+    const Length& leftMargin() const { return m_leftMargin; }
     bool isDescendantOfRoot(const Element*) const;
     void computeIntersectionObservations(double timestamp);
     void enqueueIntersectionObserverEntry(IntersectionObserverEntry&);
+    void applyRootMargin(LayoutRect&) const;
     unsigned firstThresholdGreaterThan(float ratio) const;
     void deliver();
     void setActive(bool);
     void disconnect();
     void removeObservation(IntersectionObservation&);
     bool hasEntries() const { return m_entries.size(); }
 
     DECLARE_TRACE();
 
 private:
-    explicit IntersectionObserver(IntersectionObserverCallback&, Element&, const Vector<float>& thresholds);
+    explicit IntersectionObserver(IntersectionObserverCallback&, Element&, const Vector<Length>& rootMargin, const Vector<float>& thresholds);
 
     void checkRootAndDetachIfNeeded();
 
     Member<IntersectionObserverCallback> m_callback;
     WeakPtrWillBeWeakMember<Element> m_root;
     HeapHashSet<WeakMember<IntersectionObservation>> m_observations;
     HeapVector<Member<IntersectionObserverEntry>> m_entries;
     Vector<float> m_thresholds;
+    Length m_topMargin;
+    Length m_rightMargin;
+    Length m_bottomMargin;
+    Length m_leftMargin;
 };
 
 } // namespace blink
 
 #endif // IntersectionObserver_h