net/http: update bundled http2, add tests reading response Body after Close

Updates to golang.org/x/net/http2 git rev 28273ec9 for
https://golang.org/cl/17937

Fixes #13648

Change-Id: I27c77524b2e4a172c5f8be08f6fbb0f2e2e4b200
Reviewed-on: https://go-review.googlesource.com/17938
Reviewed-by: Brad Fitzpatrick <[email protected]>
Run-TryBot: Brad Fitzpatrick <[email protected]>

Author: bradfitz

src/net/http/clientserver_test.go

@@ -597,3 +597,25 @@ func testTrailersServerToClient(t *testing.T, h2, flush bool) {
 		t.Errorf("Trailer after body read = %v; want %v", got, want)
 	}
 }
+
+// Don't allow a Body.Read after Body.Close. Issue 13648.
+func TestResponseBodyReadAfterClose_h1(t *testing.T) { testResponseBodyReadAfterClose(t, h1Mode) }
+func TestResponseBodyReadAfterClose_h2(t *testing.T) { testResponseBodyReadAfterClose(t, h2Mode) }
+
+func testResponseBodyReadAfterClose(t *testing.T, h2 bool) {
+	defer afterTest(t)
+	const body = "Some body"
+	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
+		io.WriteString(w, body)
+	}))
+	defer cst.close()
+	res, err := cst.c.Get(cst.ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	res.Body.Close()
+	data, err := ioutil.ReadAll(res.Body)
+	if len(data) != 0 || err == nil {
+		t.Fatalf("ReadAll returned %q, %v; want error", data, err)
+	}
+}