This lets godoc implementations provide a more efficient means
of getting this information, without reading files and parsing the
package docs.
This is especially important when the files themselves don't
actually exist and the VFS is synthesizing them on demand
(e.g. protocol buffer files -> their generated *.pb.go files).
This means corpus.Init can run quickly, without generating
every protocol file in a large corpus (or fetching it from a
cache).
In the future, this hook could also be used for caching the summaries of
regular packages.
R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/19440043
The exported Server becomes handlerServer, and part of Presentation
now. Presentation is also now an http.Handler with its own
internal mux (a detail, which might go away).
main.go becomes ever simpler.
R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/11505043
Brad Fitzpatrick