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 51019808646d1dd8f1c3ba3116751307e6206892..be55a80dd695c85db8b1a369eaab87a17bdfaac8 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -2110,7 +2110,11 @@ 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