We currently receive serialized JSON values over IPC and forward them to
them WebView callbacks, leaving it to the implementations of those
callbacks to parse the strings as JSON objects. This patch hoists that
parsing up to WebContentClient as soon as the IPC message is received.
This is to reduce the work needed for secondary implementations of these
callbacks (i.e. our Firefox DevTools server).
This adds a command line option to enable the DevTools server. Here, we
make the application the DevToolsDelegate to reply to requests from the
DevTools server about the state of the application.
LibWebView now knows how to launch RequestServer and ImageDecoderServer
without help from the UI, so let's move ownership of these services over
to LibWebView for de-duplication.
