Unifies ScrollView and RenderLayer to use non-shifted [minPos, maxPos] scroll offset

Source/core/platform/ScrollableArea.h

Index: Source/core/platform/ScrollableArea.h
diff --git a/Source/core/platform/ScrollableArea.h b/Source/core/platform/ScrollableArea.h
index a581a81b338f32d3b7c75ea616ee88229b415c26..8fd6ab3077f17016cce49dc754bbebec14e8ef48 100644
--- a/Source/core/platform/ScrollableArea.h
+++ b/Source/core/platform/ScrollableArea.h
@@ -175,6 +175,12 @@ public:
 
     virtual void reportMemoryUsage(MemoryObjectInfo*) const;
 
+    // Convenience functions
+    int scrollPosition(ScrollbarOrientation orientation) { return orientation == HorizontalScrollbar ? scrollPosition().x() : scrollPosition().y(); }
+    int minimumScrollPosition(ScrollbarOrientation orientation) { return orientation == HorizontalScrollbar ? minimumScrollPosition().x() : minimumScrollPosition().y(); }
+    int maximumScrollPosition(ScrollbarOrientation orientation) { return orientation == HorizontalScrollbar ? maximumScrollPosition().x() : maximumScrollPosition().y(); }
+    int clampScrollPosition(ScrollbarOrientation orientation, int pos)  { return std::max(std::min(pos, maximumScrollPosition(orientation)), minimumScrollPosition(orientation)); }
+
 protected:
     ScrollableArea();
     virtual ~ScrollableArea();