Trigger style recalc when the window's active state change

Source/core/editing/FrameSelection.cpp

Index: Source/core/editing/FrameSelection.cpp
diff --git a/Source/core/editing/FrameSelection.cpp b/Source/core/editing/FrameSelection.cpp
index b2948ef0d254de143ce815d6e4c9383fec615569..1d5db14bd502e6bb705253de596d867658b19969 100644
--- a/Source/core/editing/FrameSelection.cpp
+++ b/Source/core/editing/FrameSelection.cpp
@@ -1464,6 +1464,11 @@ void FrameSelection::focusedOrActiveStateChanged()
     bool activeAndFocused = isFocusedAndActive();
 
     RefPtrWillBeRawPtr<Document> document = m_frame->document();
+    // Invalidate All CustomScrollbars as CustomScrollbars supports
+    // CSS window-active attribute.
+    if (FrameView* view = document->view())
+        view->invalidateAllCustomScrollbarsOnActiveChanged();
+
     document->updateRenderTreeIfNeeded();
 
     // Because RenderObject::selectionBackgroundColor() and