message: docs: add changelog for 5.1.2
diff: +<a name="5.1.2"></a>
  +## [5.1.2](https://github.com/angular/angular/compare/5.1.1...5.1.2) (2017-12-20)
  +
  +
  +### Bug Fixes
  +
  +* **common:** fix a Closure compilation issue. ([267ebf3](https://github.com/angular/angular/commit/267ebf3))
  +* **compiler:** make tsx file aot compatible ([756dd34](https://github.com/angular/angular/commit/756dd34)), closes [#20555](https://github.com/angular/angular/issues/20555)
  +* **compiler:** report an error for recursive module references ([ced575f](https://github.com/angular/angular/commit/ced575f))
  +* **compiler-cli:** do not emit invalid .metadata.json files ([a1d4c2d](https://github.com/angular/angular/commit/a1d4c2d))
  +* **compiler-cli:** do not force type checking on .js files ([3b63e16](https://github.com/angular/angular/commit/3b63e16))
  +* **service-worker:** check for updates on navigation ([a33182c](https://github.com/angular/angular/commit/a33182c)), closes [#20877](https://github.com/angular/angular/issues/20877)
  +* **upgrade:** replaces get/setAngularLib with get/setAngularJSGlobal ([66cc2fa](https://github.com/angular/angular/commit/66cc2fa))
  +
  +
  +
  <a name="5.2.0-beta.0"></a>
  # [5.2.0-beta.0](https://github.com/angular/angular/compare/5.1.0...5.2.0-beta.0) (2017-12-13)
  