Use std::unique_ptr<base::Value> in V8ValueConverter.

extensions/renderer/script_injection.cc

Index: extensions/renderer/script_injection.cc
diff --git a/extensions/renderer/script_injection.cc b/extensions/renderer/script_injection.cc
index 8933f664d20c16b01cd12ec0d8cc9bace1a7593a..f867800b03f3569e402eda5954263fcaa432cc1c 100644
--- a/extensions/renderer/script_injection.cc
+++ b/extensions/renderer/script_injection.cc
@@ -292,7 +292,7 @@ void ScriptInjection::OnJsInjectionCompleted(
       // when encountered.
       v8::Local<v8::Context> context =
           render_frame_->GetWebFrame()->mainWorldScriptContext();
-      execution_result_.reset(v8_converter->FromV8Value(results[0], context));
+      execution_result_ = v8_converter->FromV8Value(results[0], context);
     }
     if (!execution_result_.get())
       execution_result_ = base::Value::CreateNullValue();