Clear m_treeBoundaryCrossingScopes when reconstructing StyleResolver.

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

Index: third_party/WebKit/Source/core/dom/StyleEngine.cpp
diff --git a/third_party/WebKit/Source/core/dom/StyleEngine.cpp b/third_party/WebKit/Source/core/dom/StyleEngine.cpp
index 2c1ab5550ef6c6a909628ea901a1c6758c288845..27d80372c8c18532a0e09e740a25d1d8ed127395 100644
--- a/third_party/WebKit/Source/core/dom/StyleEngine.cpp
+++ b/third_party/WebKit/Source/core/dom/StyleEngine.cpp
@@ -455,6 +455,8 @@ void StyleEngine::clearResolver() {
   for (TreeScope* treeScope : m_activeTreeScopes)
     treeScope->clearScopedStyleResolver();
 
+  m_treeBoundaryCrossingScopes.clear();
+
   if (m_resolver) {
     TRACE_EVENT1("blink", "StyleEngine::clearResolver", "frame",
                  document().frame());