[Fast Refresh] Add additional test case

[Timer]

This is a test that @gaearon found broken, but we had accidentally fixed for a different reason (#12671).

To prevent a regression, we're adding this test.

[ijjk]

Stats from current PR

Default Server Mode (Increase detected ⚠️)

General

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
buildDuration	12.8s	12.8s	-27ms
nodeModulesSize	59.6 MB	59.6 MB	✓

Page Load Tests Overall increase ✓

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
/ failed reqs	0	0	✓
/ total time (seconds)	2.213	2.178	-0.04
/ avg req/sec	1129.59	1147.82	⚠️ +18.23
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.465	1.418	-0.05
/error-in-render avg req/sec	1706.99	1762.74	⚠️ +55.75

Client Bundles (main, webpack, commons)

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
main-HASH.js gzip	6.67 kB	6.67 kB	✓
webpack-HASH.js gzip	746 B	746 B	✓
de003c3a9d30..5ce3.js gzip	10.4 kB	10.4 kB	✓
framework.HASH.js gzip	39.1 kB	39.1 kB	✓
Overall change	57 kB	57 kB	✓

Client Bundles (main, webpack, commons) Modern

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
main-HASH.module.js gzip	5.71 kB	5.71 kB	✓
webpack-HASH..dule.js gzip	746 B	746 B	✓
de003c3a9d30..dule.js gzip	6.85 kB	6.85 kB	✓
framework.HA..dule.js gzip	39.1 kB	39.1 kB	✓
Overall change	52.4 kB	52.4 kB	✓

Legacy Client Bundles (polyfills)

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
polyfills-HASH.js gzip	26.3 kB	26.3 kB	✓
Overall change	26.3 kB	26.3 kB	✓

Client Pages

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
_app.js gzip	1.26 kB	1.26 kB	✓
_error.js gzip	3.29 kB	3.29 kB	✓
hooks.js gzip	881 B	881 B	✓
index.js gzip	222 B	222 B	✓
link.js gzip	2.06 kB	2.06 kB	✓
routerDirect.js gzip	280 B	280 B	✓
withRouter.js gzip	278 B	278 B	✓
Overall change	8.26 kB	8.26 kB	✓

Client Pages Modern

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
_app.module.js gzip	599 B	599 B	✓
_error.module.js gzip	2.09 kB	2.09 kB	✓
hooks.module.js gzip	383 B	383 B	✓
index.module.js gzip	223 B	223 B	✓
link.module.js gzip	1.52 kB	1.52 kB	✓
routerDirect..dule.js gzip	279 B	279 B	✓
withRouter.m..dule.js gzip	278 B	278 B	✓
Overall change	5.37 kB	5.37 kB	✓

Client Build Manifests

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
_buildManifest.js gzip	61 B	61 B	✓
_buildManife..dule.js gzip	61 B	61 B	✓
Overall change	122 B	122 B	✓

Rendered Page Sizes

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
index.html gzip	928 B	928 B	✓
link.html gzip	938 B	938 B	✓
withRouter.html gzip	926 B	926 B	✓
Overall change	2.79 kB	2.79 kB	✓

---

Serverless Mode

General

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
buildDuration	14s	13.8s	-184ms
nodeModulesSize	59.6 MB	59.6 MB	✓

Client Bundles (main, webpack, commons)

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
main-HASH.js gzip	6.67 kB	6.67 kB	✓
webpack-HASH.js gzip	746 B	746 B	✓
de003c3a9d30..5ce3.js gzip	10.4 kB	10.4 kB	✓
framework.HASH.js gzip	39.1 kB	39.1 kB	✓
Overall change	57 kB	57 kB	✓

Client Bundles (main, webpack, commons) Modern

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
main-HASH.module.js gzip	5.71 kB	5.71 kB	✓
webpack-HASH..dule.js gzip	746 B	746 B	✓
de003c3a9d30..dule.js gzip	6.85 kB	6.85 kB	✓
framework.HA..dule.js gzip	39.1 kB	39.1 kB	✓
Overall change	52.4 kB	52.4 kB	✓

Legacy Client Bundles (polyfills)

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
polyfills-HASH.js gzip	26.3 kB	26.3 kB	✓
Overall change	26.3 kB	26.3 kB	✓

Client Pages

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
_app.js gzip	1.26 kB	1.26 kB	✓
_error.js gzip	3.29 kB	3.29 kB	✓
hooks.js gzip	881 B	881 B	✓
index.js gzip	222 B	222 B	✓
link.js gzip	2.06 kB	2.06 kB	✓
routerDirect.js gzip	280 B	280 B	✓
withRouter.js gzip	278 B	278 B	✓
Overall change	8.26 kB	8.26 kB	✓

Client Pages Modern

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
_app.module.js gzip	599 B	599 B	✓
_error.module.js gzip	2.09 kB	2.09 kB	✓
hooks.module.js gzip	383 B	383 B	✓
index.module.js gzip	223 B	223 B	✓
link.module.js gzip	1.52 kB	1.52 kB	✓
routerDirect..dule.js gzip	279 B	279 B	✓
withRouter.m..dule.js gzip	278 B	278 B	✓
Overall change	5.37 kB	5.37 kB	✓

Client Build Manifests

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
_buildManifest.js gzip	61 B	61 B	✓
_buildManife..dule.js gzip	61 B	61 B	✓
Overall change	122 B	122 B	✓

Serverless bundles

	zeit/next.js canary	Timer/next.js test/test-invalidate	Change
_error.js	851 kB	851 kB	✓
404.html	4.18 kB	4.18 kB	✓
hooks.html	3.81 kB	3.81 kB	✓
index.js	851 kB	851 kB	✓
link.js	888 kB	888 kB	✓
routerDirect.js	881 kB	881 kB	✓
withRouter.js	881 kB	881 kB	✓
Overall change	4.36 MB	4.36 MB	✓