Adapt and reland old position sticky implementation

third_party/WebKit/Source/core/layout/LayoutGeometryMap.h

Index: third_party/WebKit/Source/core/layout/LayoutGeometryMap.h
diff --git a/third_party/WebKit/Source/core/layout/LayoutGeometryMap.h b/third_party/WebKit/Source/core/layout/LayoutGeometryMap.h
index 39f38345ddb746d90f327c07f4bceeab3d25b25c..84037975457f70ac144b74d2e7206fbcb80f7027 100644
--- a/third_party/WebKit/Source/core/layout/LayoutGeometryMap.h
+++ b/third_party/WebKit/Source/core/layout/LayoutGeometryMap.h
@@ -74,8 +74,8 @@ public:
 
     // Push geometry info between this layoutObject and some ancestor. The ancestor must be its container() or some
     // stacking context between the layoutObject and its container.
-    void push(const LayoutObject*, const LayoutSize&, bool accumulatingTransform = false, bool isNonUniform = false, bool isFixedPosition = false, bool hasTransform = false, LayoutSize offsetForFixedPosition = LayoutSize());
-    void push(const LayoutObject*, const TransformationMatrix&, bool accumulatingTransform = false, bool isNonUniform = false, bool isFixedPosition = false, bool hasTransform = false, LayoutSize offsetForFixedPosition = LayoutSize());
+    void push(const LayoutObject*, const LayoutSize&, bool accumulatingTransform = false, bool isNonUniform = false, bool isViewportConstrained = false, bool hasTransform = false, LayoutSize offsetForFixedPosition = LayoutSize());
+    void push(const LayoutObject*, const TransformationMatrix&, bool accumulatingTransform = false, bool isNonUniform = false, bool isViewportConstrained = false, bool hasTransform = false, LayoutSize offsetForFixedPosition = LayoutSize());
 
 private:
     void mapToContainer(TransformState&, const LayoutBoxModelObject* container = nullptr) const;
@@ -85,7 +85,7 @@ private:
 
     bool hasNonUniformStep() const { return m_nonUniformStepsCount; }
     bool hasTransformStep() const { return m_transformedStepsCount; }
-    bool hasFixedPositionStep() const { return m_fixedStepsCount; }
+    bool hasViewportConstrainedStep() const { return m_viewportConstrainedStepsCount; }
 
 #ifndef NDEBUG
     void dumpSteps() const;
@@ -100,7 +100,7 @@ private:
     size_t m_insertionPosition;
     int m_nonUniformStepsCount;
     int m_transformedStepsCount;
-    int m_fixedStepsCount;
+    int m_viewportConstrainedStepsCount;
     LayoutGeometryMapSteps m_mapping;
     LayoutSize m_accumulatedOffset;
     MapCoordinatesFlags m_mapCoordinatesFlags;