Don't add duplicated line box rects into focus ring rects

Source/core/layout/LayoutInline.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 1382 matching lines @@
     {
         if (!rect.isEmpty())
             AbsoluteLayoutRectsGeneratorContext::operator()(rect);
     }
 };
 
 } // unnamed namespace
 
 void LayoutInline::addFocusRingRects(Vector<LayoutRect>& rects, const LayoutPoint& additionalOffset) const
 {
-    AbsoluteLayoutRectsIgnoringEmptyRectsGeneratorContext context(rects, additionalOffset);
-    generateLineBoxRects(context);
+    // Add line boxes only if this object is the first object of addFocusRingRects().
+    // Otherwise the parent (LayoutBlockFlow or LayoutInline) should have added line box rects
+    // covering those of this object.
+    if (rects.isEmpty()) {
+        AbsoluteLayoutRectsIgnoringEmptyRectsGeneratorContext context(rects, additionalOffset);
+        generateLineBoxRects(context);
+    }
 
     addChildFocusRingRects(rects, additionalOffset);
 
-    if (continuation()) {
-        if (continuation()->isInline())
-            continuation()->addFocusRingRects(rects, additionalOffset + (continuation()->containingBlock()->location() - containingBlock()->location()));
+    if (LayoutBoxModelObject* continuation = this->continuation()) {
+        if (continuation->isInline())
+            continuation->addFocusRingRects(rects, additionalOffset + (continuation->containingBlock()->location() - containingBlock()->location()));
         else
-            continuation()->addFocusRingRects(rects, additionalOffset + (toLayoutBox(continuation())->location() - containingBlock()->location()));
+            continuation->addFocusRingRects(rects, additionalOffset + (toLayoutBox(continuation)->location() - containingBlock()->location()));
     }
 }
 
 void LayoutInline::computeSelfHitTestRects(Vector<LayoutRect>& rects, const LayoutPoint& layerOffset) const
 {
     AbsoluteLayoutRectsGeneratorContext context(rects, layerOffset);
     generateLineBoxRects(context);
 }
 
 void LayoutInline::addAnnotatedRegions(Vector<AnnotatedRegionValue>& regions)
@@ skipping 21 matching lines @@
 }
 
 void LayoutInline::invalidateDisplayItemClients(const LayoutBoxModelObject& paintInvalidationContainer) const
 {
     LayoutBoxModelObject::invalidateDisplayItemClients(paintInvalidationContainer);
     for (InlineFlowBox* box = firstLineBox(); box; box = box->nextLineBox())
         paintInvalidationContainer.invalidateDisplayItemClientOnBacking(*box);
 }
 
 } // namespace blink