Allow use server.go for testing against local site

Gerrit had 2 different ways to serve files locally:
- start server.go web server
- start gerrit binary with --polygerrit-dev flag

Both implementations did the same handling for local files.

This change removes --polygerrit-dev flag and related java
implementation and instead a new option --dev-cdn is added.
This option enables using cdn for static content.

Change-Id: I40d4c6c048de018bc6d856c889d7ec59592282ed

polygerrit-ui/server.go

@@ -64,11 +64,12 @@ func main() {
 		log.Fatal(err)
 	}
 
-	http.Handle("/", http.FileServer(http.Dir("app")))
+	http.Handle("/", addDevHeadersMiddleware(http.FileServer(http.Dir("app"))))
 	http.Handle("/bower_components/",
-		http.FileServer(httpfs.New(zipfs.New(componentsArchive, "bower_components"))))
+		addDevHeadersMiddleware(
+			http.FileServer(httpfs.New(zipfs.New(componentsArchive, "bower_components")))))
 	http.Handle("/fonts/",
-		http.FileServer(httpfs.New(zipfs.New(fontsArchive, "fonts"))))
+		addDevHeadersMiddleware(http.FileServer(httpfs.New(zipfs.New(fontsArchive, "fonts")))))
 
 	http.HandleFunc("/index.html", handleIndex)
 	http.HandleFunc("/changes/", handleProxy)
@@ -92,6 +93,14 @@ func main() {
 	log.Fatal(http.ListenAndServe(*port, &server{}))
 }
 
+func addDevHeadersMiddleware(h http.Handler) http.Handler {
+	return http.HandlerFunc(func(writer http.ResponseWriter, req *http.Request) {
+		writer.Header().Set("Access-Control-Allow-Origin", "*")
+		writer.Header().Set("Cache-Control", "public, max-age=10, must-revalidate")
+		h.ServeHTTP(writer, req)
+	})
+}
+
 func openDataArchive(path string) (*zip.ReadCloser, error) {
 	absBinPath, err := resourceBasePath()
 	if err != nil {