Move convertViewportToWindow and convertWindowToViewport from

third_party/WebKit/Source/platform/scroll/Scrollbar.cpp

Index: third_party/WebKit/Source/platform/scroll/Scrollbar.cpp
diff --git a/third_party/WebKit/Source/platform/scroll/Scrollbar.cpp b/third_party/WebKit/Source/platform/scroll/Scrollbar.cpp
index c2744a7e4bde5d7ebff4619414c95b95648a7262..519b3b8f2d41a00f3966e146ff8896fc9dea6249 100644
--- a/third_party/WebKit/Source/platform/scroll/Scrollbar.cpp
+++ b/third_party/WebKit/Source/platform/scroll/Scrollbar.cpp
@@ -67,7 +67,7 @@ Scrollbar::Scrollbar(ScrollableArea* scrollableArea, ScrollbarOrientation orient
     // alone when sizing).
     int thickness = m_theme.scrollbarThickness(controlSize);
     if (m_hostWindow)
-        thickness = m_hostWindow->windowToViewportScalar(thickness);
+        thickness = m_hostWindow->windowToViewportScalar(*scrollableArea->getWidget(), thickness);
     Widget::setFrameRect(IntRect(0, 0, thickness, thickness));
 
     m_currentPos = scrollableAreaCurrentPos();
@@ -503,7 +503,7 @@ int Scrollbar::scrollbarThickness() const
     int thickness = orientation() == HorizontalScrollbar ? height() : width();
     if (!thickness || !m_hostWindow)
         return thickness;
-    return m_hostWindow->windowToViewportScalar(m_theme.scrollbarThickness(controlSize()));
+    return m_hostWindow->windowToViewportScalar(*m_scrollableArea->getWidget(), m_theme.scrollbarThickness(controlSize()));
 }