Invalidate Custom Scrollbars irrespective of focused frame.

Source/core/page/FocusController.cpp

Index: Source/core/page/FocusController.cpp
diff --git a/Source/core/page/FocusController.cpp b/Source/core/page/FocusController.cpp
index 61733ddb1d39229cdc54caa798018f0abb312a5c..c846333d5e3bf67392822cb8ba98eee82a27e998 100644
--- a/Source/core/page/FocusController.cpp
+++ b/Source/core/page/FocusController.cpp
@@ -725,8 +725,15 @@ void FocusController::setActive(bool active)
     m_isActive = active;
 
     Frame* frame = focusedOrMainFrame();
-    if (frame->isLocalFrame())
+    if (frame->isLocalFrame()) {
+        // Invalidate All CustomScrollbars as CustomScrollbars supports

[pdr., 2014/12/22 18:34:48]

Please rephrase this as something like the following:
        // Invalidate all custom scrollbars because they support the CSS
        // window-active attribute. This should be applied to the entire page so
        // we invalidate from the root FrameView instead of just the focused
frame.

+        // CSS window-active attribute.Irrespective of focus on frame, this
+        // needs to be applied for entire page. So invalidate from root FrameView
+        // rather than focused frame.
+        if (FrameView* view = toLocalFrame(frame)->localFrameRoot()->document()->view())
+            view->invalidateAllCustomScrollbarsOnActiveChanged();
         toLocalFrame(frame)->selection().pageActivationChanged();
+    }
 }
 
 static void updateFocusCandidateIfNeeded(FocusType type, const FocusCandidate& current, FocusCandidate& candidate, FocusCandidate& closest)