* hore: Move draggable regions implementation from NativeBrowserView into InspectableWebContentsView
The draggable regions implementation is related to WebView, so
InspectableWebContentsView is a more appropriate place to put it there.
Also, this refactoring will allow the subsequent extension of the
WebContentsView API, which will eventually replace BrowserView API.
* fix: Lint error
* fix: Adjusted owner-window
