Add web platform test for verifying first byte timing of responseStart

Verfies that the UA measures the time before the end of header parsing in responseStart by simulating a delay after writing the status line and flushing to the client. Chrome fails this test for now, but Firefox passes. Bug: 568024 Change-Id: I61569c6a5b0d8ea2f3a06cb37a3d1ed36c06d40f Reviewed-on: https://chromium-review.googlesource.com/c/1354645 Commit-Queue: Andrew Comminos <[email protected]> Reviewed-by: Nicolás Peña Moreno <[email protected]> Reviewed-by: Yoav Weiss <[email protected]> Cr-Commit-Position: refs/heads/master@{#612412}
web-platform-tests · Nov 29, 2018 · cc2a9d4 · cc2a9d4
1 parent 6911a29
commit cc2a9d4
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Showing 3 changed files with 60 additions and 5 deletions.
diff --git a/resource-timing/SyntheticResponse.py b/resource-timing/SyntheticResponse.py
@@ -4,7 +4,9 @@
 def main(request, response):
     index = request.request_path.index("?")
     args = request.request_path[index+1:].split("&")
-    headersSent = 0
+    headers = []
+    statusSent = False
+    headersSent = False
     for arg in args:
         if arg.startswith("ignored"):
             continue
@@ -13,14 +15,28 @@ def main(request, response):
         elif arg.startswith("redirect:"):
             return (302, "WEBPERF MARKETING"), [("Location", urllib.unquote(arg[9:]))], "TEST"
         elif arg.startswith("mime:"):
-            response.headers.set("Content-Type", urllib.unquote(arg[5:]))
+            headers.append(("Content-Type", urllib.unquote(arg[5:])))
         elif arg.startswith("send:"):
             text = urllib.unquote(arg[5:])
-            if headersSent == 0:
-                response.write_status_headers()
-                headersSent = 1
+
+            if not statusSent:
+                # Default to a 200 status code.
+                response.writer.write_status(200)
+                statusSent = True
+            if not headersSent:
+                for key, value in headers:
+                    response.writer.write_header(key, value)
+                response.writer.end_headers()
+                headersSent = True
 
             response.writer.write_content(text)
+        elif arg.startswith("status:"):
+            code = int(urllib.unquote(arg[7:]))
+            response.writer.write_status(code)
+            statusSent = True
+        elif arg == "flush":
+            response.writer.flush()
+
 #        else:
 #            error "  INVALID ARGUMENT %s" % arg
 
diff --git a/resource-timing/resource-timing.html b/resource-timing/resource-timing.html
@@ -2,6 +2,7 @@
 <html>
 <head>
   <title>Resource-Timing Level 1</title>
+  <meta name="timeout" content="long">
   <!-- To aid debugability, explicitly link the testharness's CSS to avoid demand
        loading it while the test executes. -->
   <script src="/resources/testharness.js"></script>

diff --git a/resource-timing/resource-timing.js b/resource-timing/resource-timing.js
@@ -224,6 +224,44 @@ window.onload =
                 });
             });
 
+        // Ensure that responseStart only measures the time up to the first few
+        // bytes of the header response. This is tested by writing an HTTP 1.1
+        // status line, followed by a flush, then a pause before the end of the
+        // headers. The tests makes sure that responseStart is not delayed by
+        // this pause.
+        [
+            { initiator: "iframe",         response: "(done)",    mime: mimeHtml },
+            { initiator: "xmlhttprequest", response: "(done)",    mime: mimeText },
+            { initiator: "script",         response: '"";',       mime: mimeScript },
+            { initiator: "link",           response: ".unused{}", mime: mimeCss },
+        ]
+        .forEach(function (template) {
+            testCases.push({
+                description: "'" + template.initiator + " " + serverStepDelay + "ms delay in headers does not affect responseStart'",
+                test: function (test) {
+                    initiateFetch(
+                        test,
+                        template.initiator,
+                        getSyntheticUrl("status:200"
+                                        + "&flush"
+                                        + "&" + serverStepDelay + "ms"
+                                        + "&mime:" + template.mime
+                                        + "&send:" + encodeURIComponent(template.response)),
+                        function (initiator, entry) {
+                            // Test that the delay between 'requestStart' and
+                            // 'responseStart' does not include the added delay
+                            // post-statusline.
+                            assert_less_than(
+                                entry.responseStart - entry.requestStart,
+                                serverStepDelay,
+                                "Delay after HTTP/1.1 status should not affect 'responseStart'.");
+
+                            test.done();
+                        });
+                    }
+                });
+            });
+
         // Function to run the next case in the queue.
         var currentTestIndex = -1;
         function runNextCase() {