net/http/httputil: fix DumpRequestOut on https URLs

Don't try to do an SSL negotiation with a *bytes.Buffer.

Fixes #3135

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/5709050

src/pkg/net/http/httputil/dump.go

@@ -59,6 +59,15 @@ func DumpRequestOut(req *http.Request, body bool) ([]byte, error) {
 		}
 	}
 
+	// Since we're using the actual Transport code to write the request,
+	// switch to http so the Transport doesn't try to do an SSL
+	// negotiation with our dumpConn and its bytes.Buffer & pipe.
+	// The wire format for https and http are the same, anyway.
+	if req.URL.Scheme == "https" {
+		defer func() { req.URL.Scheme = "https" }()
+		req.URL.Scheme = "http"
+	}
+
 	// Use the actual Transport code to record what we would send
 	// on the wire, but not using TCP.  Use a Transport with a
 	// customer dialer that returns a fake net.Conn that waits

src/pkg/net/http/httputil/dump_test.go

@@ -71,6 +71,18 @@ var dumpTests = []dumpTest{
 			"User-Agent: Go http package\r\n" +
 			"Accept-Encoding: gzip\r\n\r\n",
 	},
+
+	// Test that an https URL doesn't try to do an SSL negotiation
+	// with a bytes.Buffer and hang with all goroutines not
+	// runnable.
+	{
+		Req: *mustNewRequest("GET", "https://example.com/foo", nil),
+
+		WantDumpOut: "GET /foo HTTP/1.1\r\n" +
+			"Host: example.com\r\n" +
+			"User-Agent: Go http package\r\n" +
+			"Accept-Encoding: gzip\r\n\r\n",
+	},
 }
 
 func TestDumpRequest(t *testing.T) {