Recursively defining custom elements should not lead to redefinition

third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/dom/custom/CustomElementsRegistry.h"
 
 #include "bindings/core/v8/ExceptionState.h"
 #include "bindings/core/v8/ScriptCustomElementDefinitionBuilder.h"
 #include "core/dom/Document.h"
 #include "core/dom/ElementRegistrationOptions.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/dom/custom/CustomElement.h"
 #include "core/dom/custom/CustomElementDefinition.h"
 #include "core/dom/custom/CustomElementDefinitionBuilder.h"
 #include "core/dom/custom/V0CustomElementRegistrationContext.h"
+#include "wtf/Allocator.h"
 
 namespace blink {
 
+class CustomElementsRegistry::NameIsBeingDefined final {
+    STACK_ALLOCATED();
+    DISALLOW_IMPLICIT_CONSTRUCTORS(NameIsBeingDefined);
+public:
+    NameIsBeingDefined(
+        CustomElementsRegistry* registry,
+        const AtomicString& name)
+        : m_registry(registry)
+        , m_name(name)
+    {
+        DCHECK(!m_registry->m_namesBeingDefined.contains(name));
+        m_registry->m_namesBeingDefined.add(name);
+    }
+
+    ~NameIsBeingDefined()
+    {
+        m_registry->m_namesBeingDefined.remove(m_name);
+    }
+
+private:
+    Member<CustomElementsRegistry> m_registry;
+    const AtomicString& m_name;
+};
+
 CustomElementsRegistry* CustomElementsRegistry::create(
     V0CustomElementRegistrationContext* v0)
 {
     // TODO(dominicc): The window could install a new document; add a signal
     // when a window installs a new document to notify that V0 context, too.
     CustomElementsRegistry* registry = new CustomElementsRegistry(v0);
     if (v0)
         v0->setV1(registry);
     return registry;
 }
@@ skipping 35 matching lines @@
     if (!builder.checkConstructorIntrinsics())
         return;
 
     if (!CustomElement::isValidName(name)) {
         exceptionState.throwDOMException(
             SyntaxError,
             "\"" + name + "\" is not a valid custom element name");
         return;
     }
 
+    if (m_namesBeingDefined.contains(name)) {
+        exceptionState.throwDOMException(
+            NotSupportedError,
+            "this name is already being defined in this registry");
+        return;
+    }
+    NameIsBeingDefined defining(this, name);
+
     if (nameIsDefined(name) || v0NameIsDefined(name)) {
         exceptionState.throwDOMException(
             NotSupportedError,
             "this name has already been used with this registry");
         return;
     }
 
     if (!builder.checkConstructorNotRegistered())
         return;
 
@@ skipping 35 matching lines @@
     return m_v0->nameIsDefined(name);
 }
 
 CustomElementDefinition* CustomElementsRegistry::definitionForName(
     const AtomicString& name) const
 {
     return m_definitions.get(name);
 }
 
 } // namespace blink