Adapt and reland old position sticky implementation

third_party/WebKit/Source/core/paint/PaintLayer.h

Index: third_party/WebKit/Source/core/paint/PaintLayer.h
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.h b/third_party/WebKit/Source/core/paint/PaintLayer.h
index ce09fe09dfd1940d6f9ffd120285f3ad88fa67ee..a6ce04d3ddaf2649db85e6b34e723c1681fa4cfd 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.h
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.h
@@ -219,6 +219,7 @@ public:
     void contentChanged(ContentChangeType);
 
     void updateLayerPositionsAfterLayout();
+    void updateLayerPositionAfterFrameScroll(const DoubleSize& scrollDelta);
     void updateLayerPositionsAfterOverflowScroll(const DoubleSize& scrollDelta);
 
     PaintLayer* enclosingPaginationLayer() const { return m_enclosingPaginationLayer; }
@@ -541,7 +542,13 @@ public:
     void updateDescendantDependentCompositingInputs(const DescendantDependentCompositingInputs&);
     void didUpdateCompositingInputs();
 
-    const AncestorDependentCompositingInputs& ancestorDependentCompositingInputs() const { ASSERT(!m_needsAncestorDependentCompositingInputsUpdate); return m_ancestorDependentCompositingInputs; }
+    const AncestorDependentCompositingInputs& ancestorDependentCompositingInputs() const
+    {
+        // TODO(flackr): When we process scroll updates after compositing updates we won't be querying ancestor
+        // dependent compositing inputs while they're still needed: http://crbug.com/420741.
+        ASSERT(isAllowedToQueryCompositingState() || !m_needsAncestorDependentCompositingInputsUpdate);
+        return m_ancestorDependentCompositingInputs;
+    }
     const DescendantDependentCompositingInputs& descendantDependentCompositingInputs() const { ASSERT(!m_needsDescendantDependentCompositingInputsUpdate); return m_descendantDependentCompositingInputs; }
 
     IntRect clippedAbsoluteBoundingBox() const { return ancestorDependentCompositingInputs().clippedAbsoluteBoundingBox; }