RenderLayerScrollableArea::updateScrollCornerStyle shouldn't do work if we're using overlay scrollb…

Source/platform/scroll/ScrollableArea.cpp

Index: Source/platform/scroll/ScrollableArea.cpp
diff --git a/Source/platform/scroll/ScrollableArea.cpp b/Source/platform/scroll/ScrollableArea.cpp
index e5c157112e9bd4d49893d9e125a1f9a402d5d1f8..af06540c5bcd3a037411713aa75eaa5027163db2 100644
--- a/Source/platform/scroll/ScrollableArea.cpp
+++ b/Source/platform/scroll/ScrollableArea.cpp
@@ -319,22 +319,25 @@ void ScrollableArea::contentsResized()
 
 bool ScrollableArea::hasOverlayScrollbars() const
 {
-    return (verticalScrollbar() && verticalScrollbar()->isOverlayScrollbar())
-        || (horizontalScrollbar() && horizontalScrollbar()->isOverlayScrollbar());
+    Scrollbar* vScrollbar = verticalScrollbar();
+    if (vScrollbar && vScrollbar->isOverlayScrollbar())
+        return true;
+    Scrollbar* hScrollbar = horizontalScrollbar();
+    return hScrollbar && hScrollbar->isOverlayScrollbar();
 }
 
 void ScrollableArea::setScrollbarOverlayStyle(ScrollbarOverlayStyle overlayStyle)
 {
     m_scrollbarOverlayStyle = overlayStyle;
 
-    if (horizontalScrollbar()) {
-        ScrollbarTheme::theme()->updateScrollbarOverlayStyle(horizontalScrollbar());
-        horizontalScrollbar()->invalidate();
+    if (Scrollbar* scrollbar = horizontalScrollbar()) {
+        ScrollbarTheme::theme()->updateScrollbarOverlayStyle(scrollbar);
+        scrollbar->invalidate();
     }
 
-    if (verticalScrollbar()) {
-        ScrollbarTheme::theme()->updateScrollbarOverlayStyle(verticalScrollbar());
-        verticalScrollbar()->invalidate();
+    if (Scrollbar* scrollbar = verticalScrollbar()) {
+        ScrollbarTheme::theme()->updateScrollbarOverlayStyle(scrollbar);
+        scrollbar->invalidate();
     }
 }