Introduce CustomElementRegistry#get() method

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

 // 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.
 
 #ifndef CustomElementsRegistry_h
 #define CustomElementsRegistry_h
 
 #include "bindings/core/v8/ScopedPersistent.h"
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/CoreExport.h"
@@ skipping 25 matching lines @@
     void define(
         ScriptState*,
         const AtomicString& name,
         const ScriptValue& constructor,
         const ElementRegistrationOptions&,
         ExceptionState&);
 
     CustomElementDefinition* definitionForConstructor(
         ScriptState*,
         v8::Local<v8::Value> constructor);
+
+    ScriptValue get(ScriptState*, const AtomicString& name) const;
+
     v8::Local<v8::Object> prototype(
         ScriptState*,
         const CustomElementDefinition&);
 
     // TODO(dominicc): Remove this when V0CustomElements are removed.
     bool nameIsDefined(const AtomicString& name) const;
 
     DECLARE_TRACE();
 
 private:
     CustomElementsRegistry(const V0CustomElementRegistrationContext*);
 
     // Retrieves the Map which, given a constructor, contains the id
     // of the definition; or given an id, contains the prototype.
     // Returns true if the map was retrieved; false if the map was
     // not initialized yet.
-    v8::Local<v8::Map> idMap(ScriptState*);
+    v8::Local<v8::Map> idMap(ScriptState*) const;
 
     bool idForConstructor(
         ScriptState*,
         v8::Local<v8::Value> constructor,
         Id&) WARN_UNUSED_RETURN;
 
     bool v0NameIsDefined(const AtomicString& name);
 
     Member<const V0CustomElementRegistrationContext> m_v0;
     HeapVector<Member<CustomElementDefinition>> m_definitions;
-    HashSet<AtomicString> m_names;
+    HashMap<AtomicString, Id> m_names;
 };
 
 } // namespace blink
 
 #endif // CustomElementsRegistry_h