Add infrastructure for partial layouts

Source/core/rendering/RenderBlock.h

Index: Source/core/rendering/RenderBlock.h
diff --git a/Source/core/rendering/RenderBlock.h b/Source/core/rendering/RenderBlock.h
index 24cc7472c7b08f796ac5f23eb90d7ffc64825d03..558c43104722abca8b5b050c6b255d15280ff127 100644
--- a/Source/core/rendering/RenderBlock.h
+++ b/Source/core/rendering/RenderBlock.h
@@ -494,6 +494,9 @@ protected:
     void layoutPositionedObjects(bool relayoutChildren, bool fixedPositionObjectsOnly = false);
     void markFixedPositionObjectForLayoutIfNeeded(RenderObject* child, SubtreeLayoutScope&);
 
+    // FIXME: This should be pure virtual with an implementation in the header.

[esprehn, 2013/08/23 20:47:27]

What does that mean? pure virtual is = 0 and then how do you have an
implementation?

[pdr., 2013/08/26 05:50:40]

You can have a pure virtual with an implementation but it's not easy to do in
this case due to how we create RenderBlocks. I've just removed this comment for
now.

+    virtual bool supportsPartialLayout() const OVERRIDE { return true; };
+
     virtual void paint(PaintInfo&, const LayoutPoint&);
     virtual void paintObject(PaintInfo&, const LayoutPoint&);
     virtual void paintChildren(PaintInfo&, const LayoutPoint&);