Populate Request.URL.Path correctly.

Before, the Request.URL.Path was blank, causing the DefaultServeMux to
redirect in a loop forever.

This is the first version I've verified to work with both Firefox
Nightly and Chrome, both with their respective HTTP/2 modes enabled.

server.go

@@ -718,9 +718,14 @@ func (sc *serverConn) newWriterAndRequest() (*responseWriter, *http.Request, err
 		sc:       sc,
 		streamID: rp.stream.id,
 	}
+	url, err := url.ParseRequestURI(rp.path)
+	if err != nil {
+		// TODO: find the right error code?
+		return nil, nil, StreamError{rp.stream.id, ErrCodeProtocol}
+	}
 	req := &http.Request{
 		Method:     rp.method,
-		URL:        &url.URL{},
+		URL:        url,
 		RemoteAddr: sc.conn.RemoteAddr().String(),
 		Header:     rp.header,
 		RequestURI: rp.path,

server_test.go

@@ -294,6 +294,9 @@ func TestServer_Request_Get(t *testing.T) {
 		if r.Method != "GET" {
 			t.Errorf("Method = %q; want GET", r.Method)
 		}
+		if r.URL.Path != "/" {
+			t.Errorf("URL.Path = %q; want /", r.URL.Path)
+		}
 		if r.ContentLength != 0 {
 			t.Errorf("ContentLength = %v; want 0", r.ContentLength)
 		}
@@ -318,6 +321,24 @@ func TestServer_Request_Get(t *testing.T) {
 	})
 }
 
+func TestServer_Request_Get_PathSlashes(t *testing.T) {
+	testServerRequest(t, func(st *serverTester) {
+		st.writeHeaders(HeadersFrameParam{
+			StreamID:      1, // clients send odd numbers
+			BlockFragment: encodeHeader(t, ":path", "/%2f/"),
+			EndStream:     true, // no DATA frames
+			EndHeaders:    true,
+		})
+	}, func(r *http.Request) {
+		if r.RequestURI != "/%2f/" {
+			t.Errorf("RequestURI = %q; want /%2f/", r.RequestURI)
+		}
+		if r.URL.Path != "///" {
+			t.Errorf("URL.Path = %q; want ///", r.URL.Path)
+		}
+	})
+}
+
 // TODO: add a test with EndStream=true on the HEADERS but setting a
 // Content-Length anyway.  Should we just omit it and force it to
 // zero?