Do not call an event listener on a cloned node in svg <use>'s UA shadow tree

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

Index: third_party/WebKit/Source/core/svg/SVGUseElement.cpp
diff --git a/third_party/WebKit/Source/core/svg/SVGUseElement.cpp b/third_party/WebKit/Source/core/svg/SVGUseElement.cpp
index fe8395d9c685a788366f03faa7439430b2ec6fff..c8a31ffc6b6fb0985d4c0af31856dc2716b35632 100644
--- a/third_party/WebKit/Source/core/svg/SVGUseElement.cpp
+++ b/third_party/WebKit/Source/core/svg/SVGUseElement.cpp
@@ -442,10 +442,8 @@ void SVGUseElement::buildShadowAndInstanceTree(SVGElement& target)
 
     addReferencesToFirstDegreeNestedUseElements(target);
 
-    if (instanceTreeIsLoading()) {
-        cloneNonMarkupEventListeners();
+    if (instanceTreeIsLoading())
         return;
-    }
 
     // Assure shadow tree building was successful.
     ASSERT(m_targetElementInstance);
@@ -464,8 +462,6 @@ void SVGUseElement::buildShadowAndInstanceTree(SVGElement& target)
     m_targetElementInstance = toSVGElement(shadowTreeRootElement->firstChild());
     ASSERT(m_targetElementInstance->parentNode() == shadowTreeRootElement);
 
-    cloneNonMarkupEventListeners();
-
     // Update relative length information.
     updateRelativeLengthsInformation();
 }
@@ -548,14 +544,6 @@ void SVGUseElement::addReferencesToFirstDegreeNestedUseElements(SVGElement& targ
         addReferenceTo(useElement);
 }
 
-void SVGUseElement::cloneNonMarkupEventListeners()
-{
-    for (SVGElement& element : Traversal<SVGElement>::descendantsOf(*userAgentShadowRoot())) {
-        if (EventTargetData* data = element.correspondingElement()->eventTargetData())
-            data->eventListenerMap.copyEventListenersNotCreatedFromMarkupToTarget(&element);

[pdr., 2016/07/30 04:02:42]

With cloneNonMarkupEventListeners gone we can remove a lot of other
dubious-looking code too. Can you delete
EventListenerMap::copyEventListenersNotCreatedFromMarkupToTarget and
v8LazyEventListener's wasCreatedFromMarkup and eventListener's
wasCreatedFromMarkup?

[hayato, 2016/08/01 03:44:10]

Good point! Done. 

-    }
-}
-
 bool SVGUseElement::hasCycleUseReferencing(const SVGUseElement& use, const ContainerNode& targetInstance, SVGElement*& newTarget) const
 {
     Element* targetElement = targetElementFromIRIString(use.hrefString(), use.treeScope());