* RegisterDevToolsClientHostFor should be called right after the agent_host and
the frontend host are created.
* SetupDevToolsFrontendClient should be called before the devtools window is
going to start navigation.
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.
