Remove viewportConstrained plumbing.

sky/engine/core/page/scrolling/ScrollingCoordinator.h

Index: sky/engine/core/page/scrolling/ScrollingCoordinator.h
diff --git a/sky/engine/core/page/scrolling/ScrollingCoordinator.h b/sky/engine/core/page/scrolling/ScrollingCoordinator.h
index 7ebcebcd58a0f0500c471f618954cc25d6f63a5e..f467d50581dff89f558afd974e8e716d57fc5696 100644
--- a/sky/engine/core/page/scrolling/ScrollingCoordinator.h
+++ b/sky/engine/core/page/scrolling/ScrollingCoordinator.h
@@ -81,10 +81,9 @@ public:
     void handleWheelEventPhase(PlatformWheelEventPhase);
 #endif
 
+    // FIXME(sky): get rid of this enum.
     enum MainThreadScrollingReasonFlags {
         HasSlowRepaintObjects = 1 << 0,
-        HasViewportConstrainedObjectsWithoutSupportingFixedLayers = 1 << 1,
-        HasNonLayerViewportConstrainedObjects = 1 << 2,
     };
 
     MainThreadScrollingReasons mainThreadScrollingReasons() const;
@@ -129,8 +128,6 @@ private:
 
     void setShouldUpdateScrollLayerPositionOnMainThread(MainThreadScrollingReasons);
 
-    bool hasVisibleSlowRepaintViewportConstrainedObjects(FrameView*) const;
-
     void setShouldHandleScrollGestureOnMainThreadRegion(const Region&);
     void setTouchEventTargetRects(LayerHitTestRects&);
     void computeTouchEventTargetRects(LayerHitTestRects&);