Sync: Support multiple setup UIs.

components/browser_sync/browser/profile_sync_service.h

Index: components/browser_sync/browser/profile_sync_service.h
diff --git a/components/browser_sync/browser/profile_sync_service.h b/components/browser_sync/browser/profile_sync_service.h
index 3fecc3197fa8b306fb396ec8b051385d7a41aae3..31ad2e1bf44c9ed908e44952977ba3e45b2dc8e7 100644
--- a/components/browser_sync/browser/profile_sync_service.h
+++ b/components/browser_sync/browser/profile_sync_service.h
@@ -165,14 +165,16 @@ class EncryptedData;
 //   that control the initial sync download:
 //
 //    * SetFirstSetupComplete()
-//    * SetSetupInProgress()
+//    * GetSetupInProgressHandle()
 //
 //   SetFirstSetupComplete() should be called once the user has finished setting
-//   up sync at least once on their account. SetSetupInProgress(true) should be
-//   called while the user is actively configuring their account, and then
-//   SetSetupInProgress(false) should be called when configuration is complete.
-//   Once both these conditions have been met, CanConfigureDataTypes() will
-//   return true and datatype configuration can begin.
+//   up sync at least once on their account. GetSetupInProgressHandle() should
+//   be called while the user is actively configuring their account. The handle
+//   should be deleted once configuration is complete.
+//
+//   Once first setup has completed and there are no outstanding
+//   setup-in-progress handles, CanConfigureDataTypes() will return true and
+//   datatype configuration can begin.
 class ProfileSyncService : public sync_driver::SyncService,
                            public sync_driver::SyncFrontend,
                            public sync_driver::SyncPrefObserver,
@@ -280,7 +282,6 @@ class ProfileSyncService : public sync_driver::SyncService,
                             syncer::ModelTypeSet chosen_types) override;
   void SetFirstSetupComplete() override;
   bool IsFirstSetupInProgress() const override;
-  void SetSetupInProgress(bool setup_in_progress) override;
   bool IsSetupInProgress() const override;
   bool ConfigurationDone() const override;
   const GoogleServiceAuthError& GetAuthError() const override;
@@ -671,6 +672,9 @@ class ProfileSyncService : public sync_driver::SyncService,
   friend class TestProfileSyncService;
   FRIEND_TEST_ALL_PREFIXES(ProfileSyncServiceTest, InitialState);
 
+  // sync_driver::SyncService implementation
+  void SetSetupInProgress(bool setup_in_progress) override;
+
   // Stops the sync engine. Does NOT set IsSyncRequested to false. Use
   // RequestStop for that. |data_fate| controls whether the local sync data is
   // deleted or kept when the engine shuts down.