Fix use after free bug by calling GetTokenService in Core's ctor.

sync/internal_api/attachments/attachment_downloader_impl.cc

Index: sync/internal_api/attachments/attachment_downloader_impl.cc
diff --git a/sync/internal_api/attachments/attachment_downloader_impl.cc b/sync/internal_api/attachments/attachment_downloader_impl.cc
index 1b32e79d6d78858a754cd58d88a54bcdb4ef1903..ab34c8338904be48c13d5b6e1d261603cf540a7e 100644
--- a/sync/internal_api/attachments/attachment_downloader_impl.cc
+++ b/sync/internal_api/attachments/attachment_downloader_impl.cc
@@ -41,14 +41,14 @@ AttachmentDownloaderImpl::AttachmentDownloaderImpl(
         url_request_context_getter,
     const std::string& account_id,
     const OAuth2TokenService::ScopeSet& scopes,
-    scoped_ptr<OAuth2TokenServiceRequest::TokenServiceProvider>
+    const scoped_refptr<OAuth2TokenServiceRequest::TokenServiceProvider>&
         token_service_provider)
     : OAuth2TokenService::Consumer("attachment-downloader-impl"),
       sync_service_url_(sync_service_url),
       url_request_context_getter_(url_request_context_getter),
       account_id_(account_id),
       oauth2_scopes_(scopes),
-      token_service_provider_(token_service_provider.Pass()) {
+      token_service_provider_(token_service_provider) {
   DCHECK(!account_id.empty());
   DCHECK(!scopes.empty());
   DCHECK(token_service_provider_);