Sometimes the browser downloads the dashboard's HTML file rather than showing it

Sometimes the browser downloads the dashboard's HTML file rather than showing it

Why?

# HTTP headers when there's this problem

```
suztomo-macbookpro44% curl --output /dev/null -vvv https://storage.googleapis.com/cloud-opensource-java-dashboard/com.google.cloud/libraries-bom/snapshot/index.html
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0* Trying 142.250.72.112...
* TCP_NODELAY set
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0* Connected to storage.googleapis.com (142.250.72.112) port 443 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* successfully set certificate verify locations:
* CAfile: /etc/ssl/cert.pem
CApath: none
* TLSv1.2 (OUT), TLS handshake, Client hello (1):
} [236 bytes data]
* TLSv1.2 (IN), TLS handshake, Server hello (2):
{ [96 bytes data]
* TLSv1.2 (IN), TLS handshake, Certificate (11):
{ [2772 bytes data]
* TLSv1.2 (IN), TLS handshake, Server key exchange (12):
{ [116 bytes data]
* TLSv1.2 (IN), TLS handshake, Server finished (14):
{ [4 bytes data]
* TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
} [37 bytes data]
* TLSv1.2 (OUT), TLS change cipher, Change cipher spec (1):
} [1 bytes data]
* TLSv1.2 (OUT), TLS handshake, Finished (20):
} [16 bytes data]
* TLSv1.2 (IN), TLS change cipher, Change cipher spec (1):
{ [1 bytes data]
* TLSv1.2 (IN), TLS handshake, Finished (20):
{ [16 bytes data]
* SSL connection using TLSv1.2 / ECDHE-ECDSA-CHACHA20-POLY1305
* ALPN, server accepted to use h2
* Server certificate:
* subject: C=US; ST=California; L=Mountain View; O=Google LLC; CN=*.storage.googleapis.com
* start date: Aug 16 02:55:40 2021 GMT
* expire date: Nov 8 02:55:39 2021 GMT
* subjectAltName: host "storage.googleapis.com" matched cert's "*.googleapis.com"
* issuer: C=US; O=Google Trust Services; CN=GTS CA 1O1
* SSL certificate verify ok.
* Using HTTP2, server supports multi-use
* Connection state changed (HTTP/2 confirmed)
* Copying HTTP/2 data in stream buffer to connection buffer after upgrade: len=0
* Using Stream ID: 1 (easy handle 0x7ff2b100e800)
> GET /cloud-opensource-java-dashboard/com.google.cloud/libraries-bom/snapshot/index.html HTTP/2
> Host: storage.googleapis.com
> User-Agent: curl/7.64.1
> Accept: */*
>
* Connection state changed (MAX_CONCURRENT_STREAMS == 100)!
< HTTP/2 200
< x-guploader-uploadid: ADPycdv2BTpSFkoujZFeZTXRLmHyygD8slT5TaciF87z3mGnWjBNZMWLP6YdUrHRNxrIb9FbOKPtMeD5JIpxakGGmxuDBPuL8Q
< expires: Fri, 27 Aug 2021 19:35:08 GMT
< date: Fri, 27 Aug 2021 18:35:08 GMT
< last-modified: Thu, 26 Aug 2021 19:43:57 GMT
< etag: "2bf4ae7f7825ba1d6edce3f2b45f1104"
< x-goog-generation: 1630007037320026
< x-goog-metageneration: 1
< x-goog-stored-content-encoding: identity
< x-goog-stored-content-length: 43760
< content-type: application/octet-stream
< x-goog-hash: crc32c=3c9obQ==
< x-goog-hash: md5=K/Suf3gluh1u3OPytF8RBA==
< x-goog-storage-class: MULTI_REGIONAL
< accept-ranges: bytes
< content-length: 43760
< server: UploadServer
< age: 116
< cache-control: public, max-age=3600
< alt-svc: h3=":443"; ma=2592000,h3-29=":443"; ma=2592000,h3-T051=":443"; ma=2592000,h3-Q050=":443"; ma=2592000,h3-Q046=":443"; ma=2592000,h3-Q043=":443"; ma=2592000,quic=":443"; ma=2592000; v="46,43"
<
{ [1388 bytes data]
100 43760 100 43760 0 0 368k 0 --:--:-- --:--:-- --:--:-- 368k
* Connection #0 to host storage.googleapis.com left intact
* Closing connection 0

```

It's showing `content-type: application/octet-stream`.

# HTTP headers when it succeeds

```
suztomo-macbookpro44% curl --output /dev/null -vvv https://storage.googleapis.com/cloud-opensource-java-dashboard/com.google.cloud/libraries-bom/snapshot/index.html
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0* Trying 142.250.65.240...
* TCP_NODELAY set
* Connected to storage.googleapis.com (142.250.65.240) port 443 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* successfully set certificate verify locations:
* CAfile: /etc/ssl/cert.pem
CApath: none
* TLSv1.2 (OUT), TLS handshake, Client hello (1):
} [236 bytes data]
* TLSv1.2 (IN), TLS handshake, Server hello (2):
{ [96 bytes data]
* TLSv1.2 (IN), TLS handshake, Certificate (11):
{ [2772 bytes data]
* TLSv1.2 (IN), TLS handshake, Server key exchange (12):
{ [115 bytes data]
* TLSv1.2 (IN), TLS handshake, Server finished (14):
{ [4 bytes data]
* TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
} [37 bytes data]
* TLSv1.2 (OUT), TLS change cipher, Change cipher spec (1):
} [1 bytes data]
* TLSv1.2 (OUT), TLS handshake, Finished (20):
} [16 bytes data]
* TLSv1.2 (IN), TLS change cipher, Change cipher spec (1):
{ [1 bytes data]
* TLSv1.2 (IN), TLS handshake, Finished (20):
{ [16 bytes data]
* SSL connection using TLSv1.2 / ECDHE-ECDSA-CHACHA20-POLY1305
* ALPN, server accepted to use h2
* Server certificate:
* subject: C=US; ST=California; L=Mountain View; O=Google LLC; CN=*.storage.googleapis.com
* start date: Aug 16 02:55:40 2021 GMT
* expire date: Nov 8 02:55:39 2021 GMT
* subjectAltName: host "storage.googleapis.com" matched cert's "*.googleapis.com"
* issuer: C=US; O=Google Trust Services; CN=GTS CA 1O1
* SSL certificate verify ok.
* Using HTTP2, server supports multi-use
* Connection state changed (HTTP/2 confirmed)
* Copying HTTP/2 data in stream buffer to connection buffer after upgrade: len=0
* Using Stream ID: 1 (easy handle 0x7fa444008200)
> GET /cloud-opensource-java-dashboard/com.google.cloud/libraries-bom/snapshot/index.html HTTP/2
> Host: storage.googleapis.com
> User-Agent: curl/7.64.1
> Accept: */*
>
* Connection state changed (MAX_CONCURRENT_STREAMS == 100)!
< HTTP/2 200
< x-guploader-uploadid: ADPycdvFYKDINevd81oayagsW1gGxjaf1Q6JvUi24cZUE3vo63fKrqgfh0LJBMyiFEwrDK2pkPRLtsDYCqTWz6ZXyGk-I5DkEg
< expires: Thu, 02 Sep 2021 15:36:31 GMT
< date: Thu, 02 Sep 2021 14:36:31 GMT
< last-modified: Wed, 01 Sep 2021 19:48:12 GMT
< etag: "9c1406767725e953a6fd7ffc6da234ed"
< x-goog-generation: 1630525692134068
< x-goog-metageneration: 2
< x-goog-stored-content-encoding: identity
< x-goog-stored-content-length: 43760
< content-type: text/html
< x-goog-hash: crc32c=rZGkcw==
< x-goog-hash: md5=nBQGdncl6VOm/X/8baI07Q==
< x-goog-storage-class: MULTI_REGIONAL
< accept-ranges: bytes
< content-length: 43760
< server: UploadServer
< cache-control: public, max-age=3600
< age: 42
< alt-svc: h3=":443"; ma=2592000,h3-29=":443"; ma=2592000,h3-T051=":443"; ma=2592000,h3-Q050=":443"; ma=2592000,h3-Q046=":443"; ma=2592000,h3-Q043=":443"; ma=2592000,quic=":443"; ma=2592000; v="46,43"
<
{ [1388 bytes data]
100 43760 100 43760 0 0 534k 0 --:--:-- --:--:-- --:--:-- 534k
* Connection #0 to host storage.googleapis.com left intact
* Closing connection 0

```

It has `content-type: text/html`.