Both Android (Chrome) and iOS offer WebView SDKs that allow native applications to retrieve and render web content. The capabilities of WebView on both devices have improved significantly with the latest releases to the point of being almost on par with their respective browsers (Chrome on Android and iOS Safari).
In recent months, we have seen both the Facebook and Twitter mobile applications make a shift to rendering web content within the native application using WebView, rather than launching the device's browser.
For example, when a user clicks on a hyperlink within their Facebook feed or Twitter stream, the web site may be rendered within the application itself (depending on the version). This has implications for mobile testing of web sites.
If you are involved in developing or testing web sites, I would be interested in hearing what you currently do in terms of testing your web content on mobile WebView components.
Are you specifically testing your web site on Chrome and iOS WebView applications? Or, are you restricting testing to the mobile browsers given the recent parity of WebView functionality?