Add the text direction to the WebScrollbar interface.

Source/core/platform/ScrollableArea.cpp

Index: Source/core/platform/ScrollableArea.cpp
diff --git a/Source/core/platform/ScrollableArea.cpp b/Source/core/platform/ScrollableArea.cpp
index 8bb6bed3891e6d812b19500b789fe85da2a37dda..ff56d746baf3c77a2c8da608c8712c5bb38564c9 100644
--- a/Source/core/platform/ScrollableArea.cpp
+++ b/Source/core/platform/ScrollableArea.cpp
@@ -402,6 +402,11 @@ IntPoint ScrollableArea::clampScrollPosition(const IntPoint& scrollPosition) con
     return scrollPosition.shrunkTo(maximumScrollPosition()).expandedTo(minimumScrollPosition());
 }
 
+TextDirection ScrollableArea::textDirection() const
+{
+    return !m_scrollOrigin.x() ? LTR : RTL;
+}
+
 int ScrollableArea::lineStep(ScrollbarOrientation) const
 {
     return pixelsPerLineStep();