CustomScrollbar Style not updated for IFrame.

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 321 matching lines @@
     }
     if (m_verticalScrollbar && m_verticalScrollbar->isCustomScrollbar()) {
         m_verticalScrollbar->styleChanged();
         didStyleChange = true;
     }
     if (didStyleChange) {
         updateScrollbarGeometry();
         updateScrollCorner();
         positionScrollbarLayers();
     }
+    if (!m_parts.isEmpty())
+        recalculateWidgetCustomScrollbarStyle();
+}
+
+void FrameView::recalculateWidgetCustomScrollbarStyle()

[MuVen, 2014/12/04 15:47:10]

with this changes any scrollbar pertaining to frameView shall be invalidated.
may be using ChildrenWidgetSet m_children is better than using RenderPart
?(share your view).

The problem is with RLSA custom-scrollbar. in RLSA setHasVerticalScrollbar is
triggered on scrollbar creation and the scrollbars are not preserved, just like
in FrameView::addWidget(). May if we can store those scrollbar and call
styleChanged ? rather than entire page invalidation call ?

+{
+    WillBeHeapVector<RefPtrWillBeMember<RenderPart> > parts;
+    copyToVector(m_parts, parts);
+
+    for (size_t i = 0; i < parts.size() && renderView(); ++i) {

[skobes, 2014/12/04 17:18:38]

This looks like it does the equivalent of
FrameView::recalculateCustomScrollbarStyle on each iframe.  But
recalculateCustomScrollbarStyle is called by RenderBox::styleDidChange. 
Shouldn't this happen automatically through the style invalidation of the
iframe's document element?

[MuVen, 2014/12/04 17:50:28]

True. Instead of writing one more api i have reused
recalculateCustomScrollbarStyl from RenderPart itself. But for ::inactive we
have to write this API so that it shall invalidate on focusActive Changed.

+        Widget* widget = parts[i]->widget();
+        if (widget && widget->isFrameView()) {
+            FrameView* frameView = toFrameView(widget);
+            bool didStyleChange = false;
+            if (frameView->horizontalScrollbar() && frameView->horizontalScrollbar()->isCustomScrollbar()) {
+                frameView->horizontalScrollbar()->styleChanged();
+                didStyleChange = true;
+            }
+            if (frameView->verticalScrollbar() && frameView->verticalScrollbar()->isCustomScrollbar()) {
+                frameView->verticalScrollbar()->styleChanged();
+                didStyleChange = true;
+            }
+            if (didStyleChange) {
+                frameView->updateScrollbarGeometry();
+                frameView->updateScrollCorner();
+                frameView->positionScrollbarLayers();
+            }
+        }
+    }
 }
 
 void FrameView::recalculateScrollbarOverlayStyle()
 {
     ScrollbarOverlayStyle oldOverlayStyle = scrollbarOverlayStyle();
     ScrollbarOverlayStyle overlayStyle = ScrollbarOverlayStyleDefault;
 
     Color backgroundColor = documentBackgroundColor();
     // Reduce the background color from RGB to a lightness value
     // and determine which scrollbar style to use based on a lightness
@@ skipping 3610 matching lines @@
         return;
 
     ScrollableArea::setScrollOrigin(origin);
 
     // Update if the scroll origin changes, since our position will be different if the content size did not change.
     if (updatePositionAtAll && updatePositionSynchronously)
         updateScrollbars(scrollOffsetDouble());
 }
 
 } // namespace blink