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

Source/core/layout/LayoutObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 1062 matching lines @@
 {
     StringBuilder name;
     name.append(this->name());
 
     if (isAnonymous())
         name.append(" (anonymous)");
     // FIXME: Remove the special case for LayoutView here (requires rebaseline of all tests).
     if (isOutOfFlowPositioned() && !isLayoutView())
         name.append(" (positioned)");
     if (isRelPositioned())
-        name.append(" (relative positioned)");
+        name.append(" (relatively positioned)");

[Ian Vollick, 2015/06/30 17:56:32]

We seem to report "relative positioned" in our output (rather than relatively),
despite the name in code (I'm looking at this and TracedLayoutObject). Perhaps
this should be left alone for consistency if we're not going to update both?

[flackr, 2015/06/30 18:44:48]

Oops, didn't mean to keep this change. Originally I wasn't sure if I was going
to be able to tell the difference between relative and sticky and was going to
call this in flow positioned but we need to handle relative differently in
LayoutBoxModelObject::offsetForInFlowPosition. Restored.

+    if (isStickyPositioned())
+        name.append(" (sticky positioned)");
     if (isFloating())
         name.append(" (floating)");
     if (spannerPlaceholder())
         name.append(" (column spanner)");
 
     return name.toString();
 }
 
 String LayoutObject::debugName() const
 {
@@ skipping 860 matching lines @@
         if (blockChildrenOnly && !child->isLayoutBlock())
             continue;
 
         if (child->isLayoutFullScreen() || child->isLayoutFullScreenPlaceholder())
             continue;
 
         RefPtr<ComputedStyle> newStyle = ComputedStyle::createAnonymousStyleWithDisplay(styleRef(), child->style()->display());
 
         // Preserve the position style of anonymous block continuations as they can have relative position when
         // they contain block descendants of relative positioned inlines.
-        if (child->isRelPositioned() && toLayoutBlock(child)->isAnonymousBlockContinuation())
+        if (child->isInFlowPositioned() && toLayoutBlock(child)->isAnonymousBlockContinuation())
             newStyle->setPosition(child->style()->position());
 
         updateAnonymousChildStyle(*child, *newStyle);
 
         child->setStyle(newStyle.release());
     }
 }
 
 void LayoutObject::updateFillImages(const FillLayer* oldLayers, const FillLayer& newLayers)
 {
@@ skipping 1279 matching lines @@
         const blink::LayoutObject* root = object1;
         while (root->parent())
             root = root->parent();
         root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
     } else {
         fprintf(stderr, "Cannot showLayoutTree. Root is (nil)\n");
     }
 }
 
 #endif