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

sync/internal_api/public/attachments/attachment_uploader_impl.h

Index: sync/internal_api/public/attachments/attachment_uploader_impl.h
diff --git a/sync/internal_api/public/attachments/attachment_uploader_impl.h b/sync/internal_api/public/attachments/attachment_uploader_impl.h
index 9e02c54a2dafd48bd8974ca2b79608c4108de75d..73417694525421051d0cc1985852613fddab35c1 100644
--- a/sync/internal_api/public/attachments/attachment_uploader_impl.h
+++ b/sync/internal_api/public/attachments/attachment_uploader_impl.h
@@ -38,7 +38,7 @@ class SYNC_EXPORT AttachmentUploaderImpl : public AttachmentUploader,
           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);
   virtual ~AttachmentUploaderImpl();
 
@@ -61,7 +61,7 @@ class SYNC_EXPORT AttachmentUploaderImpl : public AttachmentUploader,
   scoped_refptr<net::URLRequestContextGetter> url_request_context_getter_;
   std::string account_id_;
   OAuth2TokenService::ScopeSet scopes_;
-  scoped_ptr<OAuth2TokenServiceRequest::TokenServiceProvider>
+  scoped_refptr<OAuth2TokenServiceRequest::TokenServiceProvider>
       token_service_provider_;
   StateMap state_map_;
   DISALLOW_COPY_AND_ASSIGN(AttachmentUploaderImpl);