Convert //ios from scoped_ptr to std::unique_ptr.

ios/chrome/browser/signin/signin_client_factory.cc

Index: ios/chrome/browser/signin/signin_client_factory.cc
diff --git a/ios/chrome/browser/signin/signin_client_factory.cc b/ios/chrome/browser/signin/signin_client_factory.cc
index 5ba3b3b7401a9901e0b5dc6393c16c778c551d44..6d596675f4d35f4557455d42db49f17469c930f7 100644
--- a/ios/chrome/browser/signin/signin_client_factory.cc
+++ b/ios/chrome/browser/signin/signin_client_factory.cc
@@ -4,6 +4,7 @@
 
 #include "ios/chrome/browser/signin/signin_client_factory.h"
 
+#include "base/memory/ptr_util.h"
 #include "base/memory/singleton.h"
 #include "components/keyed_service/core/service_access_type.h"
 #include "components/keyed_service/ios/browser_state_dependency_manager.h"
@@ -32,11 +33,11 @@ SigninClientFactory::SigninClientFactory()
 
 SigninClientFactory::~SigninClientFactory() {}
 
-scoped_ptr<KeyedService> SigninClientFactory::BuildServiceInstanceFor(
+std::unique_ptr<KeyedService> SigninClientFactory::BuildServiceInstanceFor(
     web::BrowserState* context) const {
   ios::ChromeBrowserState* chrome_browser_state =
       ios::ChromeBrowserState::FromBrowserState(context);
-  return make_scoped_ptr(new SigninClientImpl(
+  return base::WrapUnique(new SigninClientImpl(
       chrome_browser_state,
       ios::SigninErrorControllerFactory::GetForBrowserState(
           chrome_browser_state)));