CustomScrollbar Style not updated for IFrame.

Source/core/frame/FrameView.cpp

Index: Source/core/frame/FrameView.cpp
diff --git a/Source/core/frame/FrameView.cpp b/Source/core/frame/FrameView.cpp
index 80bbf1b9c1caa164c41519188afb2ff8c9b8d76d..5743b2ecf3ad03acad99f21fc5d4a52d2bd686cf 100644
--- a/Source/core/frame/FrameView.cpp
+++ b/Source/core/frame/FrameView.cpp
@@ -339,6 +339,35 @@ void FrameView::recalculateCustomScrollbarStyle()
         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()