Fix text decoding for chunk

[huozhi]

CF worker cannot write a decoded chunk

Uncaught (in response) TypeError: This TransformStream is being used as a byte stream, but received a string on its writable side. If you wish to write a string, you'll probably want to explicitly UTF-8-encode it with TextEncoder.
worker.js:61 Uncaught (in promise) TypeError: This TransformStream is being used as a byte stream, but received a string on its writable side. If you wish to write a string, you'll probably want to explicitly UTF-8-encode it with TextEncoder.
    at Object.write (worker.js:61)
    at worker.js:46

[shuding]

Let's also find a way to test this in the future.

[ijjk]

Stats from current PR

Default Build (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	huozhi/next.js fix/text-decoder	Change
buildDuration	19.7s	19.8s	⚠️ +131ms
buildDurationCached	7.5s	7.5s	-63ms
nodeModulesSize	484 MB	484 MB	⚠️ +246 B

Page Load Tests Overall increase ✓

	vercel/next.js canary	huozhi/next.js fix/text-decoder	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.906	4.059	⚠️ +0.15
/ avg req/sec	640.08	615.91	⚠️ -24.17
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.838	1.752	-0.09
/error-in-render avg req/sec	1360.05	1426.98	+66.93

Client Bundles (main, webpack)

	vercel/next.js canary	huozhi/next.js fix/text-decoder	Change
925.HASH.js gzip	179 B	179 B	✓
framework-HASH.js gzip	42 kB	42 kB	✓
main-HASH.js gzip	28.3 kB	28.3 kB	✓
webpack-HASH.js gzip	1.44 kB	1.44 kB	✓
Overall change	72 kB	72 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	huozhi/next.js fix/text-decoder	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	huozhi/next.js fix/text-decoder	Change
_app-HASH.js gzip	1.36 kB	1.36 kB	✓
_error-HASH.js gzip	192 B	192 B	✓
amp-HASH.js gzip	309 B	309 B	✓
css-HASH.js gzip	327 B	327 B	✓
dynamic-HASH.js gzip	3.04 kB	3.04 kB	✓
head-HASH.js gzip	351 B	351 B	✓
hooks-HASH.js gzip	920 B	920 B	✓
image-HASH.js gzip	5.73 kB	5.73 kB	✓
index-HASH.js gzip	263 B	263 B	✓
link-HASH.js gzip	2.36 kB	2.36 kB	✓
routerDirect..HASH.js gzip	320 B	320 B	✓
script-HASH.js gzip	392 B	392 B	✓
withRouter-HASH.js gzip	319 B	319 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	16 kB	16 kB	✓

Client Build Manifests

	vercel/next.js canary	huozhi/next.js fix/text-decoder	Change
_buildManifest.js gzip	461 B	461 B	✓
Overall change	461 B	461 B	✓

Rendered Page Sizes

	vercel/next.js canary	huozhi/next.js fix/text-decoder	Change
index.html gzip	531 B	531 B	✓
link.html gzip	543 B	543 B	✓
withRouter.html gzip	524 B	524 B	✓
Overall change	1.6 kB	1.6 kB	✓

---

Default Build with SWC (Increase detected ⚠️)

General Overall increase ⚠️

	vercel/next.js canary	huozhi/next.js fix/text-decoder	Change
buildDuration	22.3s	23.1s	⚠️ +812ms
buildDurationCached	7.6s	7.5s	-72ms
nodeModulesSize	484 MB	484 MB	⚠️ +246 B

Page Load Tests Overall increase ✓

	vercel/next.js canary	huozhi/next.js fix/text-decoder	Change
/ failed reqs	0	0	✓
/ total time (seconds)	3.953	4.158	⚠️ +0.21
/ avg req/sec	632.38	601.29	⚠️ -31.09
/error-in-render failed reqs	0	0	✓
/error-in-render total time (seconds)	1.824	1.71	-0.11
/error-in-render avg req/sec	1370.51	1461.74	+91.23

Client Bundles (main, webpack)

	vercel/next.js canary	huozhi/next.js fix/text-decoder	Change
925.HASH.js gzip	178 B	178 B	✓
framework-HASH.js gzip	42.3 kB	42.3 kB	✓
main-HASH.js gzip	28.7 kB	28.7 kB	✓
webpack-HASH.js gzip	1.45 kB	1.45 kB	✓
Overall change	72.6 kB	72.6 kB	✓

Legacy Client Bundles (polyfills)

	vercel/next.js canary	huozhi/next.js fix/text-decoder	Change
polyfills-HASH.js gzip	31 kB	31 kB	✓
Overall change	31 kB	31 kB	✓

Client Pages

	vercel/next.js canary	huozhi/next.js fix/text-decoder	Change
_app-HASH.js gzip	1.35 kB	1.35 kB	✓
_error-HASH.js gzip	179 B	179 B	✓
amp-HASH.js gzip	313 B	313 B	✓
css-HASH.js gzip	325 B	325 B	✓
dynamic-HASH.js gzip	3.02 kB	3.02 kB	✓
head-HASH.js gzip	351 B	351 B	✓
hooks-HASH.js gzip	921 B	921 B	✓
image-HASH.js gzip	5.77 kB	5.77 kB	✓
index-HASH.js gzip	261 B	261 B	✓
link-HASH.js gzip	2.44 kB	2.44 kB	✓
routerDirect..HASH.js gzip	322 B	322 B	✓
script-HASH.js gzip	393 B	393 B	✓
withRouter-HASH.js gzip	317 B	317 B	✓
85e02e95b279..7e3.css gzip	107 B	107 B	✓
Overall change	16.1 kB	16.1 kB	✓

Client Build Manifests

	vercel/next.js canary	huozhi/next.js fix/text-decoder	Change
_buildManifest.js gzip	458 B	458 B	✓
Overall change	458 B	458 B	✓

Rendered Page Sizes

	vercel/next.js canary	huozhi/next.js fix/text-decoder	Change
index.html gzip	531 B	531 B	✓
link.html gzip	546 B	546 B	✓
withRouter.html gzip	526 B	526 B	✓
Overall change	1.6 kB	1.6 kB	✓

Commit: b37e6a4