Fix column rule under invalidation

third_party/WebKit/Source/core/paint/BlockFlowPaintInvalidator.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/BlockFlowPaintInvalidator.h"
 
 #include "core/layout/LayoutBlockFlow.h"
 #include "core/paint/BoxPaintInvalidator.h"
 #include "core/paint/PaintInvalidator.h"
 
 namespace blink {
 
 PaintInvalidationReason BlockFlowPaintInvalidator::invalidatePaintIfNeeded()
 {
     PaintInvalidationReason reason = BoxPaintInvalidator(m_blockFlow, m_context).invalidatePaintIfNeeded();
 
+    // TODO(wangxianzhu): Refactor the following into invalidateDisplayItemClients().
+
     if (reason == PaintInvalidationNone || reason == PaintInvalidationDelayedFull)
         return reason;
 
     RootInlineBox* line = m_blockFlow.firstRootBox();
     if (line && line->isFirstLineStyle()) {
         // It's the RootInlineBox that paints the ::first-line background. Note that since it may be
         // expensive to figure out if the first line is affected by any ::first-line selectors at all,
         // we just invalidate it unconditionally which is typically cheaper.
         m_blockFlow.invalidateDisplayItemClient(*line, reason);
     }
+
+    if (m_blockFlow.multiColumnFlowThread()) {
+        // Invalidate child LayoutMultiColumnSets which may need to repaint column rules after
+        // m_blockFlow's column rule style and/or layout changed.
+        for (LayoutObject* child = m_blockFlow.firstChild(); child; child = child->nextSibling()) {
+            if (child->isLayoutMultiColumnSet() && !child->shouldDoFullPaintInvalidation())
+                m_blockFlow.invalidateDisplayItemClient(*child, reason);
+        }
+    }
+
     return reason;
 }
 
 } // namespace blink