Support delayed HTTP responses in MetricIntegrationTest.

Bug: 1045064
Change-Id: I49a454e4333c3f32a5516e632901ff368ddbe729
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2065322Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Commit-Queue: Steve Kobes <skobes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#743146}

chrome/browser/page_load_metrics/integration_tests/metric_integration_test.cc

@@ -19,6 +19,7 @@ using base::CommandLine;
 using base::OnceClosure;
 using base::RunLoop;
 using base::StringPiece;
+using base::TimeDelta;
 using base::trace_event::TraceConfig;
 using content::TracingController;
 using content::WebContents;
@@ -43,10 +44,16 @@ void MetricIntegrationTest::SetUpOnMainThread() {
   histogram_tester_.emplace();
 }
 
+void MetricIntegrationTest::ServeDelayed(const std::string& url,
+                                         const std::string& content,
+                                         TimeDelta delay) {
+  embedded_test_server()->RegisterRequestHandler(
+      base::BindRepeating(&HandleRequest, url, content, delay));
+}
+
 void MetricIntegrationTest::Serve(const std::string& url,
                                   const std::string& content) {
-  embedded_test_server()->RegisterRequestHandler(
-      base::BindRepeating(&HandleRequest, url, content));
+  ServeDelayed(url, content, TimeDelta());
 }
 
 void MetricIntegrationTest::Start() {
@@ -106,9 +113,12 @@ void MetricIntegrationTest::SetUpCommandLine(CommandLine* command_line) {
 std::unique_ptr<HttpResponse> MetricIntegrationTest::HandleRequest(
     const std::string& relative_url,
     const std::string& content,
+    TimeDelta delay,
     const HttpRequest& request) {
   if (request.relative_url != relative_url)
     return nullptr;
+  if (!delay.is_zero())
+    base::PlatformThread::Sleep(delay);
   auto response = std::make_unique<BasicHttpResponse>();
   response->set_code(net::HTTP_OK);
   response->set_content(content);

chrome/browser/page_load_metrics/integration_tests/metric_integration_test.h

@@ -49,6 +49,11 @@ class MetricIntegrationTest : public InProcessBrowserTest {
   // type of "text/html; charset=utf-8".
   void Serve(const std::string& url, const std::string& content);
 
+  // Like Serve, but with an artificial time delay in the response.
+  void ServeDelayed(const std::string& url,
+                    const std::string& content,
+                    base::TimeDelta delay);
+
   // Starts the test server.  Call this after configuring request
   // handlers, and before loading any pages.
   void Start();
@@ -90,6 +95,7 @@ class MetricIntegrationTest : public InProcessBrowserTest {
   static std::unique_ptr<net::test_server::HttpResponse> HandleRequest(
       const std::string& relative_url,
       const std::string& content,
+      base::TimeDelta delay,
       const net::test_server::HttpRequest& request);
 
   base::Optional<ukm::TestAutoSetUkmRecorder> ukm_recorder_;