Fix the way <title> is read under <use> shadow tree

third_party/WebKit/Source/core/svg/SVGUseElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Nikolas Zimmermann
  * <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007 Rob Buis <buis@kde.org>
  * Copyright (C) Research In Motion Limited 2009-2010. All rights reserved.
  * Copyright (C) 2011 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  * Copyright (C) 2012 University of Szeged
  * Copyright (C) 2012 Renata Hodovan <reni@webkit.org>
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 22 matching lines @@
 #include "core/dom/StyleChangeReason.h"
 #include "core/dom/TaskRunnerHelper.h"
 #include "core/dom/shadow/ElementShadow.h"
 #include "core/dom/shadow/ShadowRoot.h"
 #include "core/events/Event.h"
 #include "core/layout/svg/LayoutSVGTransformableContainer.h"
 #include "core/svg/SVGGElement.h"
 #include "core/svg/SVGLengthContext.h"
 #include "core/svg/SVGSVGElement.h"
 #include "core/svg/SVGSymbolElement.h"
+#include "core/svg/SVGTitleElement.h"
 #include "core/svg/SVGTreeScopeResources.h"
 #include "core/xml/parser/XMLDocumentParser.h"
 #include "platform/loader/fetch/FetchRequest.h"
 #include "platform/loader/fetch/ResourceFetcher.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 inline SVGUseElement::SVGUseElement(Document& document)
     : SVGGraphicsElement(SVGNames::useTag, document),
@@ skipping 279 matching lines @@
     return;
   Element* target = resolveTargetElement();
   if (target && target->isSVGElement()) {
     buildShadowAndInstanceTree(toSVGElement(*target));
     invalidateDependentShadowTrees();
   }
 
   ASSERT(!m_needsShadowTreeRecreation);
 }
 
+String SVGUseElement::title() const {
+  // Find the first <title> child in <use> which doesn't cover shadow tree.
+  if (Element* titleElement = Traversal<SVGTitleElement>::firstChild(*this))
+    return titleElement->innerText();
+
+  // If there is no <title> child in <use>, we lookup first <title> child in
+  // shadow tree.
+  if (Element* titleElement =
+          Traversal<SVGTitleElement>::firstChild(*m_targetElementInstance))
+    return titleElement->innerText();
+
+  // Otherwise return a null/empty string.

[fs, 2017/02/28 09:07:15]

null/empty -> null

(String() is a null string, for an empty string use emptyString.)

+  return String();
+}
+
 static void associateCorrespondingElements(SVGElement& targetRoot,
                                            SVGElement& instanceRoot) {
   auto targetRange = Traversal<SVGElement>::inclusiveDescendantsOf(targetRoot);
   auto targetIterator = targetRange.begin();
   for (SVGElement& instance :
        Traversal<SVGElement>::inclusiveDescendantsOf(instanceRoot)) {
     ASSERT(!instance.correspondingElement());
     instance.setCorrespondingElement(&*targetIterator);
     ++targetIterator;
   }
@@ skipping 372 matching lines @@
 
   if (m_resource)
     m_resource->removeClient(this);
 
   m_resource = resource;
   if (m_resource)
     m_resource->addClient(this);
 }
 
 }  // namespace blink