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

Source/core/paint/DeprecatedPaintLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 768 matching lines @@
     }
 
     // Subtract our parent's scroll offset.
     if (DeprecatedPaintLayer* positionedParent = layoutObject()->isOutOfFlowPositioned() ? enclosingPositionedAncestor() : nullptr) {
         // For positioned layers, we subtract out the enclosing positioned layer's scroll offset.
         if (positionedParent->layoutObject()->hasOverflowClip()) {
             IntSize offset = positionedParent->layoutBox()->scrolledContentOffset();
             localPoint -= offset;
         }
 
-        if (positionedParent->layoutObject()->isRelPositioned() && positionedParent->layoutObject()->isLayoutInline()) {
+        if (positionedParent->layoutObject()->isInFlowPositioned() && positionedParent->layoutObject()->isLayoutInline()) {
             LayoutSize offset = toLayoutInline(positionedParent->layoutObject())->offsetForInFlowPositionedInline(*toLayoutBox(layoutObject()));
             localPoint += offset;
         }
     } else if (parent() && parent()->layoutObject()->hasOverflowClip()) {
         IntSize scrollOffset = parent()->layoutBox()->scrolledContentOffset();
         localPoint -= scrollOffset;
     }
 
     bool positionOrOffsetChanged = false;
-    if (layoutObject()->isRelPositioned()) {
+    if (layoutObject()->isInFlowPositioned()) {
         LayoutSize newOffset = layoutObject()->offsetForInFlowPosition();
         positionOrOffsetChanged = newOffset != m_offsetForInFlowPosition;
         m_offsetForInFlowPosition = newOffset;
         localPoint.move(m_offsetForInFlowPosition);
     } else {
         m_offsetForInFlowPosition = LayoutSize();
     }
 
     // FIXME: We'd really like to just get rid of the concept of a layer rectangle and rely on the layoutObjects.
     localPoint.moveBy(-inlineBoundingBoxOffset);
@@ skipping 1931 matching lines @@
 
 void showLayerTree(const blink::LayoutObject* layoutObject)
 {
     if (!layoutObject) {
         fprintf(stderr, "Cannot showLayerTree. Root is (nil)\n");
         return;
     }
     showLayerTree(layoutObject->enclosingLayer());
 }
 #endif