Add root margin support for IntersectionObserver.

third_party/WebKit/Source/core/dom/IntersectionObservation.cpp

 // 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.
 
 #include "core/dom/IntersectionObservation.h"
 
 #include "core/dom/ElementRareData.h"
 #include "core/dom/IntersectionObserver.h"
 #include "core/frame/FrameView.h"
 #include "core/layout/LayoutBox.h"
@@ skipping 27 matching lines @@
 {
     // Map and clip rect into root element coordinates.
     // TODO(szager): the writing mode flipping needs a test.
     ASSERT(m_target);
     LayoutObject* rootLayoutObject = m_observer->rootLayoutObject();
     LayoutObject* targetLayoutObject = m_target->layoutObject();
     targetLayoutObject->mapToVisibleRectInAncestorSpace(toLayoutBoxModelObject(rootLayoutObject), rect, nullptr);
     if (rootLayoutObject->hasOverflowClip()) {
         LayoutBox* rootLayoutBox = toLayoutBox(rootLayoutObject);
         LayoutRect clipRect(LayoutPoint(), LayoutSize(rootLayoutBox->layer()->size()));
+        m_observer->applyRootMargin(clipRect);
         rootLayoutBox->flipForWritingMode(rect);
         rect.intersect(clipRect);
         rootLayoutBox->flipForWritingMode(rect);
     }
 }
 
 void IntersectionObservation::clipToFrameView(IntersectionGeometry& geometry)
 {
     Element* rootElement = m_observer->root();
     LayoutObject* rootLayoutObject = m_observer->rootLayoutObject();
     if (rootElement == rootElement->document().documentElement()) {
         geometry.rootRect = LayoutRect(rootElement->document().view()->visibleContentRect());
+        m_observer->applyRootMargin(geometry.rootRect);
         geometry.intersectionRect.intersect(geometry.rootRect);
     } else {
         if (rootLayoutObject->isBox())
             geometry.rootRect = LayoutRect(toLayoutBox(rootLayoutObject)->absoluteContentBox());
         else
             geometry.rootRect = LayoutRect(rootLayoutObject->absoluteBoundingBoxRect());
+        m_observer->applyRootMargin(geometry.rootRect);

[ojan, 2016/01/12 01:08:49]

Nit: you are repeating this line in both the if and else clauses. Can you have a
single line after the else clause on line 70?

[szager1, 2016/01/12 19:24:43]

applyRootMargin has to happen before the call to
geometry.intersectionRect.intersect(geometry.rootRect) in the 'if' clause, so I
don't think there's a clean way to refactor it.

     }
 
     LayoutPoint scrollPosition(rootElement->document().view()->scrollPosition());
     geometry.targetRect.moveBy(-scrollPosition);
     geometry.intersectionRect.moveBy(-scrollPosition);
     geometry.rootRect.moveBy(-scrollPosition);
 }
 
 static void mapRectToDocumentCoordinates(LayoutObject& layoutObject, LayoutRect& rect)
 {
@@ skipping 78 matching lines @@
     m_observer.clear();
 }
 
 DEFINE_TRACE(IntersectionObservation)
 {
     visitor->trace(m_observer);
     visitor->trace(m_target);
 }
 
 } // namespace blink