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

ios/chrome/browser/signin/signin_client_factory.h

Index: ios/chrome/browser/signin/signin_client_factory.h
diff --git a/ios/chrome/browser/signin/signin_client_factory.h b/ios/chrome/browser/signin/signin_client_factory.h
index aec8a12b1756d375b01dbd536e080cfcd83296d0..42c6b077c571dceb3d3b8a8ca662085f86f71e2f 100644
--- a/ios/chrome/browser/signin/signin_client_factory.h
+++ b/ios/chrome/browser/signin/signin_client_factory.h
@@ -5,8 +5,9 @@
 #ifndef IOS_CHROME_BROWSER_SIGNIN_SIGNIN_CLIENT_FACTORY_H_
 #define IOS_CHROME_BROWSER_SIGNIN_SIGNIN_CLIENT_FACTORY_H_
 
+#include <memory>
+
 #include "base/macros.h"
-#include "base/memory/scoped_ptr.h"
 #include "components/keyed_service/ios/browser_state_keyed_service_factory.h"
 
 namespace base {
@@ -35,7 +36,7 @@ class SigninClientFactory : public BrowserStateKeyedServiceFactory {
   ~SigninClientFactory() override;
 
   // BrowserStateKeyedServiceFactory implementation.
-  scoped_ptr<KeyedService> BuildServiceInstanceFor(
+  std::unique_ptr<KeyedService> BuildServiceInstanceFor(
       web::BrowserState* context) const override;
 
   DISALLOW_COPY_AND_ASSIGN(SigninClientFactory);