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

ios/chrome/browser/history/web_history_service_factory.h

Index: ios/chrome/browser/history/web_history_service_factory.h
diff --git a/ios/chrome/browser/history/web_history_service_factory.h b/ios/chrome/browser/history/web_history_service_factory.h
index c2a067a0e0de09c8e123cf9fb2ea5e74861ca5d6..7207ab6acd778aac4b04e9aec74a340a61ff91f7 100644
--- a/ios/chrome/browser/history/web_history_service_factory.h
+++ b/ios/chrome/browser/history/web_history_service_factory.h
@@ -5,8 +5,9 @@
 #ifndef IOS_CHROME_BROWSER_HISTORY_WEB_HISTORY_SERVICE_FACTORY_H_
 #define IOS_CHROME_BROWSER_HISTORY_WEB_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 {
@@ -37,7 +38,7 @@ class WebHistoryServiceFactory : public BrowserStateKeyedServiceFactory {
   ~WebHistoryServiceFactory() override;
 
   // BrowserStateKeyedServiceFactory implementation.
-  scoped_ptr<KeyedService> BuildServiceInstanceFor(
+  std::unique_ptr<KeyedService> BuildServiceInstanceFor(
       web::BrowserState* context) const override;
 
   DISALLOW_COPY_AND_ASSIGN(WebHistoryServiceFactory);