Hover over for functions does not give much information

Hovering over a function name during debugging displays `function() { [native code] }` for web , while VM version displays text of the actual function body,

Need to figure out how to give more useful information to the user.

See https://github.com/Dart-Code/Dart-Code/issues/2518 for repro steps and snapshots.

Start with the reproduction steps and snapshots in Dart-Code/Dart-Code issue 2518, comparing the web debugger's hover output with the VM version. Identify the debugging entry point responsible for function hover display; done means web hovers provide more useful function information than `function() { [native code] }`.

Written by the indexing model from the issue text.