WebView supports a subset of Chrome's policies, that can be set via the App Restrictions mechanism. They are read on the embedder app itself rather than from a centralized location. That gives administrator more flexibility and granularity, but to apply a global policy, it has to be set separately on each app.
The policies will be applied to WebViews used inside the targeted apps without having to modify the apps themselves. No special WebView APIs have been added to expose policy information. If developers want to change their app's behavior depending on that, they can read them as they have access to the App Restrictions.
Please see the Policy List on chromium.org for more information and the list of supported policies.