[Content] Update V8ValueConverter::create to return a std::unique_ptr

components/plugins/renderer/loadable_plugin_placeholder.cc

Index: components/plugins/renderer/loadable_plugin_placeholder.cc
diff --git a/components/plugins/renderer/loadable_plugin_placeholder.cc b/components/plugins/renderer/loadable_plugin_placeholder.cc
index 41ff1b0e6dfe358a6824315af5529d6cadf186b5..c5b3b05876df0216448419a7fb0687cac305160b 100644
--- a/components/plugins/renderer/loadable_plugin_placeholder.cc
+++ b/components/plugins/renderer/loadable_plugin_placeholder.cc
@@ -343,13 +343,11 @@ void LoadablePluginPlaceholder::DidFinishIconRepositionForTestingCallback() {
   blink::WebElement element = plugin()->Container()->GetElement();
   element.SetAttribute("placeholderReady", "true");
 
-  std::unique_ptr<content::V8ValueConverter> converter(
-      content::V8ValueConverter::create());
   base::Value value("placeholderReady");
   blink::WebSerializedScriptValue message_data =
       blink::WebSerializedScriptValue::Serialize(
           blink::MainThreadIsolate(),
-          converter->ToV8Value(
+          content::V8ValueConverter::Create()->ToV8Value(
               &value,
               element.GetDocument().GetFrame()->MainWorldScriptContext()));
   blink::WebDOMMessageEvent msg_event(message_data);