Caches the scrollbar's thickness for the given theme and control size

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 84b5b4099679a7c7426243db0c27b62b94999579..253a1925ce53be4a27a18a31f9f621c7897d52a3 100644
--- a/third_party/WebKit/Source/platform/scroll/Scrollbar.cpp
+++ b/third_party/WebKit/Source/platform/scroll/Scrollbar.cpp
@@ -69,6 +69,7 @@ Scrollbar::Scrollbar(ScrollableArea* scrollableArea,
   // scrollbars (rather than leaving one dimension of the scrollbar alone when
   // sizing).
   int thickness = m_theme.scrollbarThickness(controlSize);
+  m_themeScrollbarThickness = thickness;

[oshima, 2016/10/14 23:17:30]

don't you have to cache for each controlSize?

[malaykeshav, 2016/10/14 23:18:54]

For a given scrollbar instance the ControlSize does not change. It is
initialized in the constructor.

   if (m_hostWindow)
     thickness = m_hostWindow->windowToViewportScalar(thickness);
   Widget::setFrameRect(IntRect(0, 0, thickness, thickness));
@@ -526,8 +527,7 @@ 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_themeScrollbarThickness);
 }
 
 bool Scrollbar::isOverlayScrollbar() const {