Currently, if a client hint request header is set by the JavaScript, and later by Chromium, then the two values are concatenated together.  e.g.,
dpr: 2.0, 3.4

However, for a given client hint header, the spec allows only one value to be set. 

We need to ensure that the client hint request header contains at most one value. Additionally, if the value is set using JavaScript, then Chromium should not override that value.