Handle nested position:sticky elements

third_party/WebKit/public/platform/WebLayerStickyPositionConstraint.h

Index: third_party/WebKit/public/platform/WebLayerStickyPositionConstraint.h
diff --git a/third_party/WebKit/public/platform/WebLayerStickyPositionConstraint.h b/third_party/WebKit/public/platform/WebLayerStickyPositionConstraint.h
index 296496d76f24a22d2545fa38c5d5c6555e31f2ef..0e768f11127f65132ed6f6b20aba933ad8fbd254 100644
--- a/third_party/WebKit/public/platform/WebLayerStickyPositionConstraint.h
+++ b/third_party/WebKit/public/platform/WebLayerStickyPositionConstraint.h
@@ -31,6 +31,8 @@
 
 namespace blink {
 
+class WebLayer;
+
 // TODO(flackr): Combine with WebLayerPositionConstraint.
 struct WebLayerStickyPositionConstraint {
   // True if the layer is sticky.
@@ -62,6 +64,11 @@ struct WebLayerStickyPositionConstraint {
   // element should not be shifted beyond.
   WebRect scrollContainerRelativeContainingBlockRect;
 
+  WebLayer* nearestLayerShiftingStickyBox;
+  WebLayer* nearestLayerShiftingContainingBlock;
+
+  WebFloatSize cachedComputedStickyOffset;
+
   WebLayerStickyPositionConstraint()
       : isSticky(false),
         isAnchoredLeft(false),
@@ -71,7 +78,9 @@ struct WebLayerStickyPositionConstraint {
         leftOffset(0.f),
         rightOffset(0.f),
         topOffset(0.f),
-        bottomOffset(0.f) {}
+        bottomOffset(0.f),
+        nearestLayerShiftingStickyBox(nullptr),
+        nearestLayerShiftingContainingBlock(nullptr) {}
 };
 
 }  // namespace blink