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 43ca7e6f9bbb99b9699b3b314fb8cb23c2a066c2..cef87e53de3961978e24c79f7b9d523db09cdefa 100644
--- a/third_party/WebKit/Source/core/style/ComputedStyle.h
+++ b/third_party/WebKit/Source/core/style/ComputedStyle.h
@@ -475,7 +475,7 @@ 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(); }