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 5ba8c9e67888f603299f7d4b135cbb416a488b70..4b0b7b6654f9b27757e0a1910e78b97ba03960b0 100644
--- a/Source/core/platform/ScrollableArea.h
+++ b/Source/core/platform/ScrollableArea.h
@@ -174,6 +174,12 @@ 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();