Add position: sticky as supported position value when CSSStickyPosition is enabled.

Source/core/layout/TracedLayoutObject.cpp

 // Copyright 2015 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 "config.h"
 #include "core/layout/TracedLayoutObject.h"
 
 #include "core/layout/LayoutInline.h"
 #include "core/layout/LayoutTableCell.h"
 #include "core/layout/LayoutText.h"
@@ skipping 13 matching lines @@
     RefPtr<JSONObject> json(toJSON());
     json->writeJSON(&builder);
     return builder.toString();
 }
 
 TracedLayoutObject::TracedLayoutObject(const LayoutObject& object)
     : m_address((unsigned long) &object)
     , m_isAnonymous(object.isAnonymous())
     , m_isPositioned(object.isOutOfFlowPositioned())
     , m_isRelPositioned(object.isRelPositioned())
+    , m_isStickyPositioned(object.isStickyPositioned())
     , m_isFloating(object.isFloating())
     , m_selfNeeds(object.selfNeedsLayout())
     , m_positionedMovement(object.needsPositionedMovementLayout())
     , m_childNeeds(object.normalChildNeedsLayout())
     , m_posChildNeeds(object.posChildNeedsLayout())
     , m_isTableCell(object.isTableCell())
     , m_name(String(object.name()).isolatedCopy())
     , m_absRect(object.absoluteBoundingBoxRect())
 {
     if (Node* node = object.node()) {
@@ skipping 74 matching lines @@
         json->setNumber("col", m_col);
         if (m_rowSpan != 1)
             json->setNumber("rowSpan", m_rowSpan);
         if (m_colSpan != 1)
             json->setNumber("colSpan", m_colSpan);
     }
     if (m_isAnonymous)
         json->setBoolean("anonymous", m_isAnonymous);
     if (m_isRelPositioned)
         json->setBoolean("relativePositioned", m_isRelPositioned);
+    if (m_isStickyPositioned)
+        json->setBoolean("stickyPositioned", m_isStickyPositioned);
     if (m_isFloating)
         json->setBoolean("float", m_isFloating);
     if (m_children.size()) {
         RefPtr<JSONArray> children(JSONArray::create());
         for (const auto& child : m_children) {
             children->pushObject(child->toJSON());
         }
         json->setArray("children", children);
     }
     return json.release();
 }
 
 } // namespace blink