Its possible for sync to be suppressed before the user attempts one-click

chrome/browser/ui/sync/one_click_signin_sync_starter.cc

Index: chrome/browser/ui/sync/one_click_signin_sync_starter.cc
diff --git a/chrome/browser/ui/sync/one_click_signin_sync_starter.cc b/chrome/browser/ui/sync/one_click_signin_sync_starter.cc
index 62e8019a6a9767e19c8cfe8aa81c78124ece84c5..79ccfd3a8e186259eddb817b419edd661242aad4 100644
--- a/chrome/browser/ui/sync/one_click_signin_sync_starter.cc
+++ b/chrome/browser/ui/sync/one_click_signin_sync_starter.cc
@@ -9,6 +9,7 @@
 #include "chrome/browser/signin/signin_manager_factory.h"
 #include "chrome/browser/sync/profile_sync_service.h"
 #include "chrome/browser/sync/profile_sync_service_factory.h"
+#include "chrome/browser/sync/sync_prefs.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/webui/signin/login_ui_service.h"
 #include "chrome/browser/ui/webui/signin/login_ui_service_factory.h"
@@ -24,11 +25,17 @@ OneClickSigninSyncStarter::OneClickSigninSyncStarter(
       start_mode_(start_mode) {
   DCHECK(browser_);
 
-  ProfileSyncService* profile_sync_service =
-      ProfileSyncServiceFactory::GetForProfile(browser_->profile());
   // Let the sync service know that setup is in progress so it doesn't start
   // syncing until the user has finished any configuration.
+  ProfileSyncService* profile_sync_service =
+      ProfileSyncServiceFactory::GetForProfile(browser_->profile());
   profile_sync_service->SetSetupInProgress(true);
+
+  // Make sure the syncing is not suppressed, otherwise the SigninManager
+  // will not be able to compelte sucessfully.
+  browser_sync::SyncPrefs sync_prefs(browser_->profile()->GetPrefs());
+  sync_prefs.SetStartSuppressed(false);
+
   SigninManager* manager = SigninManagerFactory::GetForProfile(
       browser_->profile());
   manager->StartSignInWithCredentials(session_index, email, password);
@@ -56,7 +63,6 @@ void OneClickSigninSyncStarter::SigninSuccess() {
     // Just kick off the sync machine, no need to configure it first.
     profile_sync_service->SetSyncSetupCompleted();
     profile_sync_service->SetSetupInProgress(false);
-    profile_sync_service->UnsuppressAndStart();
   } else {
     // Give the user a chance to configure things. We don't clear the
     // ProfileSyncService::setup_in_progress flag because we don't want sync