Improve docs

impl/prod/context.go

Index: impl/prod/context.go
diff --git a/impl/prod/context.go b/impl/prod/context.go
index 401e10ef5a2f5a1583a8e4841bb5bc0bc8a287c4..6193547f90ce4d610b2755500fe35fffb9e9bf60 100644
--- a/impl/prod/context.go
+++ b/impl/prod/context.go
@@ -5,10 +5,14 @@
 package prod
 
 import (
+	"net/http"
+
 	"golang.org/x/net/context"
+	"google.golang.org/appengine"
 )
 
-// Use adds production implementations for all the gae services to the context.
+// Use adds production implementations for all the gae services to the context,
+// using the existing context obtained by appengine.NewContext.
 //
 // The services added are:
 //   - github.com/luci/gae/service/rawdatastore
@@ -22,3 +26,18 @@ import (
 func Use(c context.Context) context.Context {
 	return useRDS(useMC(useTQ(useGI(c))))
 }
+
+// Use adds production implementations for all the gae services to the context.
+//
+// The services added are:
+//   - github.com/luci/gae/service/rawdatastore
+//   - github.com/luci/gae/service/taskqueue
+//   - github.com/luci/gae/service/memcache
+//   - github.com/luci/gae/service/info
+//
+// These can be retrieved with the <service>.Get functions.
+//
+// The implementations are all backed by the real appengine SDK functionality,
+func UseRequest(r *http.Request) context.Context {
+	return useRDS(useMC(useTQ(useGI(appengine.NewContext(r)))))
+}