Introduce CustomElementRegistry#get() method

third_party/WebKit/Source/bindings/core/v8/ScriptCustomElementDefinition.h

Index: third_party/WebKit/Source/bindings/core/v8/ScriptCustomElementDefinition.h
diff --git a/third_party/WebKit/Source/bindings/core/v8/ScriptCustomElementDefinition.h b/third_party/WebKit/Source/bindings/core/v8/ScriptCustomElementDefinition.h
index 96f76ddb79f1c827f9ad3a1c40ead2f8e21aaffc..b069cdb8c4907e3dd1fb6fcedb55ee80bb25ee5f 100644
--- a/third_party/WebKit/Source/bindings/core/v8/ScriptCustomElementDefinition.h
+++ b/third_party/WebKit/Source/bindings/core/v8/ScriptCustomElementDefinition.h
@@ -45,6 +45,9 @@ private:
         const v8::Local<v8::Object>& constructor,
         const v8::Local<v8::Object>& prototype);
 
+    // Implementations of |CustomElementDefinition|
+    ScriptValue getConstructor(ScriptState*) final;

[dominicc (has gone to gerrit), 2016/05/31 06:01:50]

Because ScriptCustomElementDefinition will need to vend callbacks, I think it
should have RefPtr<ScriptState> and simply use that.

[yosin_UTC9, 2016/05/31 09:16:57]

We should have |ScriptState*| here to verify we use |SCE| with valid context.

+
     ScopedPersistent<v8::Object> m_constructor;
     ScopedPersistent<v8::Object> m_prototype;
 };