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 728d112e7ea9fb724c88316c23fc6f57c8aaccf1..c659a7e6ba82873be6b984d4407a800481484713 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(); }