Add UMA for how long service workers run for.

content/browser/service_worker/service_worker_lifetime_tracker_unittest.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/browser/service_worker/service_worker_lifetime_tracker.h"
+
+#include "base/test/histogram_tester.h"
+#include "base/test/simple_test_tick_clock.h"
+#include "base/time/tick_clock.h"
+#include "content/public/test/test_utils.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace content {
+
+class ServiceWorkerLifetimeTrackerTest : public testing::Test {
+ public:
+  ServiceWorkerLifetimeTrackerTest()
+      : tick_clock_(new base::SimpleTestTickClock()),
+        tracker_(base::WrapUnique(tick_clock_)) {}
+
+  base::SimpleTestTickClock* tick_clock() { return tick_clock_; }
+  ServiceWorkerLifetimeTracker* tracker() { return &tracker_; }
+
+ private:
+  // Not owned.
+  base::SimpleTestTickClock* tick_clock_;
+
+  ServiceWorkerLifetimeTracker tracker_;
+};
+
+TEST_F(ServiceWorkerLifetimeTrackerTest, Metrics) {
+  int64_t kVersion1 = 13;  // dummy value
+  int64_t kVersion2 = 14;  // dummy value
+
+  tick_clock()->SetNowTicks(base::TimeTicks::Now());
+
+  // Start a worker.
+  tracker()->StartTiming(kVersion2);
+
+  // Run a worker for 10 seconds.
+  {
+    base::HistogramTester metrics;
+    tracker()->StartTiming(kVersion1);
+    tick_clock()->Advance(base::TimeDelta::FromSeconds(10));
+    tracker()->StopTiming(kVersion1);
+    metrics.ExpectTimeBucketCount("ServiceWorker.Runtime",
+                                  base::TimeDelta::FromSeconds(10), 1);
+  }
+
+  // Advance 10 minutes and stop the worker. It should record Runtime.
+  {
+    base::HistogramTester metrics;
+    tick_clock()->Advance(base::TimeDelta::FromMinutes(10));
+    tracker()->StopTiming(kVersion2);
+    metrics.ExpectTimeBucketCount(
+        "ServiceWorker.Runtime",
+        base::TimeDelta::FromMinutes(10) + base::TimeDelta::FromSeconds(10), 1);
+  }
+
+  {
+    base::HistogramTester metrics;
+    // Start a worker and abort the timing.
+    tracker()->StartTiming(kVersion1);
+    tick_clock()->Advance(base::TimeDelta::FromSeconds(10));
+    tracker()->AbortTiming(kVersion1);
+
+    // Aborting multiple times should be fine.
+    tracker()->AbortTiming(kVersion1);
+    tracker()->AbortTiming(kVersion1);
+    // StopTiming should not record a timing.
+    tracker()->StopTiming(kVersion1);
+    tracker()->StopTiming(kVersion1);
+
+    metrics.ExpectTotalCount("ServiceWorker.Runtime", 0);
+  }
+}
+
+}  // namespace content