net/http/pprof: include Symbol in Index

Fixes #69897

Change-Id: I5887f34504b39018e16f269e087b43bc6a80964b
Reviewed-on: https://go-review.googlesource.com/c/go/+/620455
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

Author: seankhliao

src/net/http/pprof/pprof.go

@@ -367,6 +367,7 @@ var profileDescriptions = map[string]string{
 	"heap":         "A sampling of memory allocations of live objects. You can specify the gc GET parameter to run GC before taking the heap sample.",
 	"mutex":        "Stack traces of holders of contended mutexes",
 	"profile":      "CPU profile. You can specify the duration in the seconds GET parameter. After you get the profile file, use the go tool pprof command to investigate the profile.",
+	"symbol":       "Maps given program counters to function names. Counters can be specifed in a GET raw query or POST body, multiple counters are separated by '+'.",
 	"threadcreate": "Stack traces that led to the creation of new OS threads",
 	"trace":        "A trace of execution of the current program. You can specify the duration in the seconds GET parameter. After you get the trace file, use the go tool trace command to investigate the trace.",
 }
@@ -404,7 +405,7 @@ func Index(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// Adding other profiles exposed from within this package
-	for _, p := range []string{"cmdline", "profile", "trace"} {
+	for _, p := range []string{"cmdline", "profile", "symbol", "trace"} {
 		profiles = append(profiles, profileEntry{
 			Name: p,
 			Href: p,