Switch SupportsUserData uses to use unique_ptr.

ios/clean/chrome/app/steps/root_coordinator+application_step.mm

Index: ios/clean/chrome/app/steps/root_coordinator+application_step.mm
diff --git a/ios/clean/chrome/app/steps/root_coordinator+application_step.mm b/ios/clean/chrome/app/steps/root_coordinator+application_step.mm
index a0d3af9d2e458af0f3afee55df90f331e21c3ada..c6041a24bc6528f7e8ecb661b9b540878a2c12de 100644
--- a/ios/clean/chrome/app/steps/root_coordinator+application_step.mm
+++ b/ios/clean/chrome/app/steps/root_coordinator+application_step.mm
@@ -4,6 +4,7 @@
 
 #import "ios/clean/chrome/app/steps/root_coordinator+application_step.h"
 
+#include "base/memory/ptr_util.h"
 #import "base/supports_user_data.h"
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
 #import "ios/chrome/browser/web_state_list/web_state_list.h"
@@ -73,8 +74,9 @@ const char kRootCoordinatorContainerKey[] = "root_coordinator";
   state.window.hidden = NO;
 
   // Make sure this object stays alive.
-  state.persistentState->SetUserData(kRootCoordinatorContainerKey,
-                                     new RootCoordinatorContainer(self));
+  state.persistentState->SetUserData(
+      kRootCoordinatorContainerKey,
+      base::MakeUnique<RootCoordinatorContainer>(self));
 
   // Add a termination step to remove this object.
   [[state terminationSteps] addObject:[[StopRootCoordinator alloc] init]];