net/http: update bundled http2 for ErrAbortHandler support, document …

…it more

Updates http2 to x/net/http2 git rev 0e2717d for:

   http2: conditionally log stacks from panics in Server Handlers like net/http
   https://golang.org/cl/33102

Fixes #17790

Change-Id: Idd3f0c65540398d41b412a33f1d80de3f7f31409
Reviewed-on: https://go-review.googlesource.com/33103
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>

src/net/http/clientserver_test.go

@@ -1189,9 +1189,6 @@ func testInterruptWithPanic(t *testing.T, h2 bool, panicValue interface{}) {
 		if gotLog == "" {
 			return
 		}
-		if h2 {
-			t.Skip("TODO: make http2.Server respect ErrAbortHandler")
-		}
 		t.Fatalf("want no log output; got: %s", gotLog)
 	}
 	if gotLog == "" {

src/net/http/server.go

@@ -75,7 +75,9 @@ var (
 // If ServeHTTP panics, the server (the caller of ServeHTTP) assumes
 // that the effect of the panic was isolated to the active request.
 // It recovers the panic, logs a stack trace to the server error log,
-// and hangs up the connection.
+// and hangs up the connection. To abort a handler so the client sees
+// an interrupted response but the server doesn't log an error, panic
+// with the value ErrAbortHandler.
 type Handler interface {
 	ServeHTTP(ResponseWriter, *Request)
 }