Convert //extensions/browser/api from scoped_ptr to std::unique_ptr

extensions/browser/api/serial/serial_apitest.cc

Index: extensions/browser/api/serial/serial_apitest.cc
diff --git a/extensions/browser/api/serial/serial_apitest.cc b/extensions/browser/api/serial/serial_apitest.cc
index f56ff94345c17d9b9175a042ad434927b06cb589..40ee4e919f0ecab13aa5be3385b651d50cb9b6f5 100644
--- a/extensions/browser/api/serial/serial_apitest.cc
+++ b/extensions/browser/api/serial/serial_apitest.cc
@@ -138,7 +138,7 @@ void CreateTestSerialServiceOnFileThread(
       io_handler_factory,
       content::BrowserThread::GetMessageLoopProxyForThread(
           content::BrowserThread::IO));
-  scoped_ptr<device::SerialDeviceEnumerator> device_enumerator(
+  std::unique_ptr<device::SerialDeviceEnumerator> device_enumerator(
       new FakeSerialDeviceEnumerator);
   new device::SerialServiceImpl(
       connection_factory, std::move(device_enumerator), std::move(request));