CustomScrollbar Style not updated for IFrame.

Source/core/rendering/RenderPart.cpp

Index: Source/core/rendering/RenderPart.cpp
diff --git a/Source/core/rendering/RenderPart.cpp b/Source/core/rendering/RenderPart.cpp
index c6557fc331bd6cff4595b624ce20a61b19135031..1b041abc1567f654fcf271b3df19f7361fa45616 100644
--- a/Source/core/rendering/RenderPart.cpp
+++ b/Source/core/rendering/RenderPart.cpp
@@ -209,6 +209,10 @@ void RenderPart::styleDidChange(StyleDifference diff, const RenderStyle* oldStyl
     if (!widget)
         return;
 
+    // If the iframe has custom scrollbars, recalculate their style.
+    if (widget && widget->isFrameView())
+        toFrameView(widget)->recalculateCustomScrollbarStyle();
+
     if (style()->visibility() != VISIBLE) {
         widget->hide();
     } else {