Adapt and reland old position sticky implementation

public/platform/WebLayer.h

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 14 matching lines @@
 
 #ifndef WebLayer_h
 #define WebLayer_h
 
 #include "WebBlendMode.h"
 #include "WebColor.h"
 #include "WebCommon.h"
 #include "WebCompositorAnimation.h"
 #include "WebDoublePoint.h"
 #include "WebFloatPoint3D.h"
+#include "WebLayerPositionConstraint.h"
 #include "WebPoint.h"
 #include "WebRect.h"
 #include "WebScrollBlocksOn.h"
 #include "WebSize.h"
 #include "WebString.h"
 #include "WebVector.h"
 
 class SkMatrix44;
 class SkImageFilter;
 
 namespace blink {
 class WebCompositorAnimationDelegate;
 class WebFilterOperations;
 class WebLayerClient;
 class WebLayerScrollClient;
 struct WebFloatPoint;
 struct WebLayerPositionConstraint;
+struct WebLayerStickyPositionConstraint;
 
 class WebLayer {
 public:
     virtual ~WebLayer() { }
 
     // Returns a positive ID that will be unique across all WebLayers allocated in this process.
     virtual int id() const = 0;
 
     // Sets a region of the layer as invalid, i.e. needs to update its content.
     virtual void invalidateRect(const WebRect&) = 0;
@@ skipping 151 matching lines @@
     virtual WebScrollBlocksOn scrollBlocksOn() const { return WebScrollBlocksOnNone; }
 
     virtual void setIsContainerForFixedPositionLayers(bool) = 0;
     virtual bool isContainerForFixedPositionLayers() const = 0;
 
     // This function sets layer position constraint. The constraint will be used
     // to adjust layer position during threaded scrolling.
     virtual void setPositionConstraint(const WebLayerPositionConstraint&) = 0;
     virtual WebLayerPositionConstraint positionConstraint() const = 0;
 
+    // FIXME: Make pure once cc is updated.
+    virtual void setStickyPositionConstraint(const WebLayerStickyPositionConstraint&) { };
+    virtual WebLayerStickyPositionConstraint stickyPositionConstraint() const { return WebLayerStickyPositionConstraint(); }
+
     // The scroll client is notified when the scroll position of the WebLayer
     // changes. Only a single scroll client can be set for a WebLayer at a time.
     // The WebLayer does not take ownership of the scroll client, and it is the
     // responsibility of the client to reset the layer's scroll client before
     // deleting the scroll client.
     virtual void setScrollClient(WebLayerScrollClient*) = 0;
 
     // Forces this layer to use a render surface. There is no benefit in doing
     // so, but this is to facilitate benchmarks and tests.
     virtual void setForceRenderSurface(bool) = 0;
 
     // True if the layer is not part of a tree attached to a WebLayerTreeView.
     virtual bool isOrphan() const = 0;
 
     virtual void setWebLayerClient(WebLayerClient*) = 0;
 };
 
 } // namespace blink
 
 #endif // WebLayer_h