Introduce CustomElementRegistry#get() method

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

Index: third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.h
diff --git a/third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.h b/third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.h
index de7d2aaa98ccb722181a7683df4dfefd92421b95..7058cc1dd0acfc36acd71443fa017494ee8dcec8 100644
--- a/third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.h
+++ b/third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.h
@@ -43,6 +43,9 @@ public:
     CustomElementDefinition* definitionForConstructor(
         ScriptState*,
         v8::Local<v8::Value> constructor);
+
+    ScriptValue get(ScriptState*, const AtomicString& name) const;
+
     v8::Local<v8::Object> prototype(
         ScriptState*,
         const CustomElementDefinition&);
@@ -59,7 +62,7 @@ private:
     // 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*,
@@ -70,7 +73,7 @@ private:
 
     Member<const V0CustomElementRegistrationContext> m_v0;
     HeapVector<Member<CustomElementDefinition>> m_definitions;
-    HashSet<AtomicString> m_names;
+    HashMap<AtomicString, Id> m_names;
 };
 
 } // namespace blink