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

ios/chrome/browser/history/history_service_factory.h

Index: ios/chrome/browser/history/history_service_factory.h
diff --git a/ios/chrome/browser/history/history_service_factory.h b/ios/chrome/browser/history/history_service_factory.h
index 6f3523a09738df8c62f917fcb7c6eb51e8a02799..c6f2e4745718cfc4e63eb819d91c6ec69ab58f02 100644
--- a/ios/chrome/browser/history/history_service_factory.h
+++ b/ios/chrome/browser/history/history_service_factory.h
@@ -5,8 +5,9 @@
 #ifndef IOS_CHROME_BROWSER_HISTORY_HISTORY_SERVICE_FACTORY_H_
 #define IOS_CHROME_BROWSER_HISTORY_HISTORY_SERVICE_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 {
@@ -43,7 +44,7 @@ class HistoryServiceFactory : public BrowserStateKeyedServiceFactory {
   ~HistoryServiceFactory() override;
 
   // BrowserStateKeyedServiceFactory implementation.
-  scoped_ptr<KeyedService> BuildServiceInstanceFor(
+  std::unique_ptr<KeyedService> BuildServiceInstanceFor(
       web::BrowserState* context) const override;
   web::BrowserState* GetBrowserStateToUse(
       web::BrowserState* context) const override;