After the BRYInspectableWebContentsView is added as subview to other
NSWindow owned by users, the view_ would not be dealloc when the web
contents got destroyed, which made the devtools window a ghost.
This class can be used to create a content::WebContents that can be inspected
by the Chrome Dev Tools. This requires embedding applications to copy
content_shell.pak into their resource bundle.
Right now the dev tools are always docked to the bottom of the view; we don't
yet support undocking or changing the docked side.
Fixes#1.
