x/tools/cmd/heapview: break out init code

This change breaks out the code that adds handler funcs and
starts the HTTP server into separate functions, so that they
can be overridden in other environments, such as Google's.

For instance, listenAndServe can be overridden in an init method
in a different file to use a HTTP2 server.

Updates golang/go#16410

Change-Id: I074242af10486c60c374e9ac7ebe9d0e61a8fa22
Reviewed-on: https://go-review.googlesource.com/25273
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
1 file changed