Correct overlay scrollbar check FrameView::scrollbarExistenceDidChange

third_party/WebKit/Source/core/frame/FrameView.cpp

Index: third_party/WebKit/Source/core/frame/FrameView.cpp
diff --git a/third_party/WebKit/Source/core/frame/FrameView.cpp b/third_party/WebKit/Source/core/frame/FrameView.cpp
index 91c82bdcf3276ac701da5bd92e86ee05da3e6acf..1079021bdb748b2e9db6d2e912f3673a5bb2b5f9 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -2121,7 +2121,11 @@ void FrameView::scrollbarExistenceDidChange() {
   if (!frame().view())
     return;
 
-  bool usesOverlayScrollbars = ScrollbarTheme::theme().usesOverlayScrollbars();
+  Element* customScrollbarElement = nullptr;
+
+  bool usesOverlayScrollbars =
+      ScrollbarTheme::theme().usesOverlayScrollbars() &&
+      !shouldUseCustomScrollbars(customScrollbarElement);
 
   // FIXME: this call to layout() could be called within FrameView::layout(),
   // but before performLayout(), causing double-layout. See also