Feed ScrollableArea::showOverlayScrollbars into ScrollbarAnimationController.

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

Index: third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp b/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
index 3991c98d2696fe08eea50d91aad7f86f8ab37be9..af89b4faa00b1eb7369b3ab6a6d2b49b5089af2a 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
+++ b/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
@@ -67,7 +67,8 @@ ScrollableArea::ScrollableArea()
       m_scrollCornerNeedsPaintInvalidation(false),
       m_scrollbarsHidden(false),
       m_scrollbarCaptured(false),
-      m_mouseOverScrollbar(false) {}
+      m_mouseOverScrollbar(false),
+      m_needsShowScrollbarLayers(false) {}
 
 ScrollableArea::~ScrollableArea() {}
 
@@ -565,6 +566,7 @@ void ScrollableArea::showOverlayScrollbars() {
     return;
 
   setScrollbarsHidden(false);
+  m_needsShowScrollbarLayers = true;
 
   const double timeUntilDisable =
       ScrollbarTheme::theme().overlayScrollbarFadeOutDelaySeconds() +