[Sync] Clear access token on shutdown

components/browser_sync/browser/profile_sync_service.cc

Index: components/browser_sync/browser/profile_sync_service.cc
diff --git a/components/browser_sync/browser/profile_sync_service.cc b/components/browser_sync/browser/profile_sync_service.cc
index 3b8bf73520ce2a66c0ca6d6d1c26bb54b05b74e0..ba286155b608730a24209f61e7786ed6d5c4f63b 100644
--- a/components/browser_sync/browser/profile_sync_service.cc
+++ b/components/browser_sync/browser/profile_sync_service.cc
@@ -898,6 +898,7 @@ void ProfileSyncService::ShutdownImpl(syncer::ShutdownReason reason) {
   encrypted_types_ = syncer::SyncEncryptionHandler::SensitiveTypes();
   passphrase_required_reason_ = syncer::REASON_PASSPHRASE_NOT_REQUIRED;
   catch_up_configure_in_progress_ = false;
+  access_token_.clear();
   request_access_token_retry_timer_.Stop();
   // Revert to "no auth error".
   if (last_auth_error_.state() != GoogleServiceAuthError::NONE)