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..b96f13a9fd9d037dff4f0d6469226b4f19217ea7 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);
+
     v8::Local<v8::Object> prototype(
         ScriptState*,
         const CustomElementDefinition&);
@@ -56,9 +59,11 @@ 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.
+    // of the definition; or given an id, contains v8::Array to hold
+    // JavaScript values of custom element definitions, e.g. constructor,
+    // prototype, promise for CER#whenDefined, and so on.
+    // TODO(yosin): Once traceWrapper is ready we should move JavaScript
+    // value to |CustomElementDefinition|.
     v8::Local<v8::Map> idMap(ScriptState*);
 
     bool idForConstructor(
@@ -70,7 +75,7 @@ private:
 
     Member<const V0CustomElementRegistrationContext> m_v0;
     HeapVector<Member<CustomElementDefinition>> m_definitions;
-    HashSet<AtomicString> m_names;
+    HashMap<AtomicString, Id> m_names;
 };
 
 } // namespace blink