Adapt and reland old position sticky implementation

third_party/WebKit/Source/core/style/ComputedStyle.h

Index: third_party/WebKit/Source/core/style/ComputedStyle.h
diff --git a/third_party/WebKit/Source/core/style/ComputedStyle.h b/third_party/WebKit/Source/core/style/ComputedStyle.h
index c4f0ede35f0eab737422471c78fdadbbc3db2db8..869c8f80354edd2428458c819b82b8aede796719 100644
--- a/third_party/WebKit/Source/core/style/ComputedStyle.h
+++ b/third_party/WebKit/Source/core/style/ComputedStyle.h
@@ -477,7 +477,7 @@ public:
     EPosition position() const { return static_cast<EPosition>(noninherited_flags.position); }
     bool hasOutOfFlowPosition() const { return position() == AbsolutePosition || position() == FixedPosition; }
     bool hasInFlowPosition() const { return position() == RelativePosition || position() == StickyPosition; }
-    bool hasViewportConstrainedPosition() const { return position() == FixedPosition; }
+    bool hasViewportConstrainedPosition() const { return position() == FixedPosition || position() == StickyPosition; }
     EFloat floating() const { return static_cast<EFloat>(noninherited_flags.floating); }
 
     const Length& width() const { return m_box->width(); }