The origin trial component implements browser-side support for origin trials.
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This component is meant to supplement the implementation that exists in Blink, by supplying an implementation for persistent origin trials.
NOTE: The implementation is currently limited to supporting persistent origin trials, and users who need to check non-persistent origin trials in the browser should continue to use one of the methods listed in http://crbug.com/1227440#c0.
The code is implemented as a component since it needs to be shared between content embedders. It is exposed to the browser process through the content::OriginTrialsControllerDelegate interface, which can be accessed from subclasses of content::BrowserContext. This interface provides access to methods to determine if a given persistent origin trial is currently enabled for a given domain.
Since persistent origin trials are considered to be enabled until the next page load for a given domain, the enablement status is not linked to any individual browser tab, unlike regular origin trials.
A server can set the Critical-Origin-Trial: <trial name> HTTP header on responses as a way to make the browser restart the request immediately if the indicated trial was not already enabled on the first request. In order to take advantage of this, the server must also provide a valid trial token for the origin trial in the Origin-Trial: <valid trial token> header, so the browser can enable the trial before restart.
The Critical-Origin-Trial header can be set multiple times.
If the headers do not include a valid trial token, a request for restart will be ignored.