Introduce Node::containingTreeScope(), which asserts that the node's root is a tree scope

third_party/WebKit/Source/core/dom/SelectorQuery.cpp

Index: third_party/WebKit/Source/core/dom/SelectorQuery.cpp
diff --git a/third_party/WebKit/Source/core/dom/SelectorQuery.cpp b/third_party/WebKit/Source/core/dom/SelectorQuery.cpp
index facc59beef3a63cb3c3f468998d53c18b46c81bd..9fc5886c2acef31281dde655c4feeca57445cec5 100644
--- a/third_party/WebKit/Source/core/dom/SelectorQuery.cpp
+++ b/third_party/WebKit/Source/core/dom/SelectorQuery.cpp
@@ -259,8 +259,8 @@ void SelectorDataList::findTraverseRootsAndExecute(ContainerNode& rootNode, type
     bool startFromParent = false;
 
     for (const CSSSelector* selector = m_selectors[0]; selector; selector = selector->tagHistory()) {
-        if (selector->match() == CSSSelector::Id && !rootNode.treeScope().containsMultipleElementsWithId(selector->value())) {
-            Element* element = rootNode.treeScope().getElementById(selector->value());
+        if (selector->match() == CSSSelector::Id && rootNode.isInTreeScope() && !rootNode.containingTreeScope().containsMultipleElementsWithId(selector->value())) {
+            Element* element = rootNode.containingTreeScope().getElementById(selector->value());
             ContainerNode* adjustedNode = &rootNode;
             if (element && (isTreeScopeRoot(rootNode) || element->isDescendantOf(&rootNode)))
                 adjustedNode = element;