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

third_party/WebKit/Source/core/events/EventPath.cpp

Index: third_party/WebKit/Source/core/events/EventPath.cpp
diff --git a/third_party/WebKit/Source/core/events/EventPath.cpp b/third_party/WebKit/Source/core/events/EventPath.cpp
index 91eb910123dbf79a5181116ccee8aea8c401d926..f45763f5d32e21fd5622a1432e1c86937a8eff29 100644
--- a/third_party/WebKit/Source/core/events/EventPath.cpp
+++ b/third_party/WebKit/Source/core/events/EventPath.cpp
@@ -35,6 +35,7 @@
 #include "core/events/TouchEvent.h"
 #include "core/events/TouchEventContext.h"
 #include "core/html/HTMLSlotElement.h"
+#include "core/svg/SVGUseElement.h"
 
 namespace blink {
 
@@ -76,15 +77,23 @@ void EventPath::initializeWith(Node& node, Event* event)
     initialize();
 }
 
-static inline bool eventPathShouldBeEmptyFor(Node& node)
+static inline bool isInSVGUseShadowTree(Node& node)
 {
-    return node.isPseudoElement() && !node.parentElement();
+    if (ShadowRoot* root = node.containingShadowRoot())
+        return root->type() == ShadowRootType::UserAgent && isSVGUseElement(root->host());
+    return false;
+}
+
+static inline bool eventPathShouldBeEmptyFor(Node& node, Event* event)
+{
+    return (node.isPseudoElement() && !node.parentElement()) || (isInSVGUseShadowTree(node) && event && !event->composed());

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

WDYT of breaking these two complex cases apart as if statements?

if (node.isPseudoElement() && !node.parentElement())
    return true;

// Exclude non-composed events from SVG use trees.
if (node.isSVGElement()) {
    if (toSVGElement(node).inUseShadowTree() && event && !event->composed())
        return true;
}

return false;

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

Sounds nice. Done

 }
 
 void EventPath::initialize()
 {
-    if (eventPathShouldBeEmptyFor(*m_node))
+    if (eventPathShouldBeEmptyFor(*m_node, m_event))
         return;
+
     calculatePath();
     calculateAdjustedTargets();
     calculateTreeOrderAndSetNearestAncestorClosedTree();
@@ -102,6 +111,12 @@ void EventPath::calculatePath()
     // storing it in a perfectly sized m_nodeEventContexts Vector.
     HeapVector<Member<Node>, 64> nodesInPath;
     Node* current = m_node;
+
+    // Exclude nodes in SVG <use>'s shadow tree from event path.
+    // See crbug.com/630870
+    while (isInSVGUseShadowTree(*current))

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

I think this can be rewritten using existing apis to avoid having to add
isInSVGUseShadowTree:
while (current->isSVGElement()) {
    SVGUseElement* correspondingUseElement =
toSVGElement(current)->correspondingUseElement();
    if (!correspondingUseElement)
        break;
    current = correspondingUseElement;
}

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

Thanks! Done.

+        current = &current->containingShadowRoot()->host();
+
     nodesInPath.append(current);
     while (current) {
         if (m_event && current->keepEventInNode(m_event))