ipn/ipnlocal: start implementing web server bits of serve

Updates tailscale/corp#7515

Change-Id: I96f4016161ba3c370492da941274c6d9a234c2bb
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

ipn/ipn_view.go

@@ -285,11 +285,13 @@ func (v *HTTPHandlerView) UnmarshalJSON(b []byte) error {
 
 func (v HTTPHandlerView) Path() string  { return v.ж.Path }
 func (v HTTPHandlerView) Proxy() string { return v.ж.Proxy }
+func (v HTTPHandlerView) Text() string  { return v.ж.Text }
 
 // A compilation failure here means this code must be regenerated, with the command at the top of this file.
 var _HTTPHandlerViewNeedsRegeneration = HTTPHandler(struct {
 	Path  string
 	Proxy string
+	Text  string
 }{})
 
 // View returns a readonly view of WebServerConfig.