Angular 5.0.0-beta.7 i18n extraction not working #19198

[x] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[ ] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question

ng new test-proj
cd test-proj
ng generate component i18n-test
echo "<p i18n>Hello world</p>" > ./src/app/i18n-test/i18n-test.component.html
npm run ng -- xi18n
stat src/messages.xlf # file exists
rm src/messages.xlf
# update to beta.6
npm i @angular/{animations,common,compiler,core,forms,http,platform-browser,platform-browser-dynamic,router,compiler-cli,language-service}@5.0.0-beta.6 typescript@2.5.1
npm run ng -- xi18n
stat src/messages.xlf # file exists
rm src/messages.xlf
# update to beta.7
npm i @angular/{animations,common,compiler,core,forms,http,platform-browser,platform-browser-dynamic,router,compiler-cli,language-service}@5.0.0-beta.7 typescript@2.5.1
npm run ng -- xi18n
stat src/messages.xlf # file does not exist

Angular version: 5.0.0-beta.7


Browser:
- [ ] Chrome (desktop) version XX
- [ ] Chrome (Android) version XX
- [ ] Chrome (iOS) version XX
- [ ] Firefox version XX
- [ ] Safari (desktop) version XX
- [ ] Safari (iOS) version XX
- [ ] IE version XX
- [ ] Edge version XX
 
For Tooling issues:
- Node version: v6.11.1
- Platform:  Windows 

Others: