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

Source/core/layout/LayoutObject.cpp

Index: Source/core/layout/LayoutObject.cpp
diff --git a/Source/core/layout/LayoutObject.cpp b/Source/core/layout/LayoutObject.cpp
index abd4d61201124cc82585b605cd753adc344d9950..ea75b689bfb73f6473bace0edddd142c0e530b6d 100644
--- a/Source/core/layout/LayoutObject.cpp
+++ b/Source/core/layout/LayoutObject.cpp
@@ -1080,7 +1080,9 @@ String LayoutObject::decoratedName() const
     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())
@@ -1961,7 +1963,7 @@ void LayoutObject::propagateStyleToAnonymousChildren(bool blockChildrenOnly)
 
         // 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);