Treat clock updates to never add a negative usage window.

Bug: 899980
Change-Id: I196999915290fe07322d934423430a0782c7ba55
Reviewed-on: https://chromium-review.googlesource.com/c/1330224Reviewed-by: Sergey Poromov <poromov@chromium.org>
Commit-Queue: Henrique Grandinetti <hgrandinetti@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607732}

chrome/browser/chromeos/policy/device_status_collector.cc

@@ -1190,8 +1190,19 @@ void DeviceStatusCollector::UpdateChildUsageTime() {
   }
 
   if (!last_active_check_.is_null() && last_state_active_) {
-    activity_storage_->AddActivityPeriod(last_active_check_, now, now,
-                                         GetUserForActivityReporting());
+    // If it's been too long since the last report, or if the activity is
+    // negative (which can happen when the clock changes), assume a single
+    // interval of activity. This is the same strategy used to enterprise users.
+    base::TimeDelta active_seconds = now - last_active_check_;
+    if (active_seconds < base::TimeDelta::FromSeconds(0) ||
+        active_seconds >= (2 * kUpdateChildActiveTimeInterval)) {
+      activity_storage_->AddActivityPeriod(now - kUpdateChildActiveTimeInterval,
+                                           now, now,
+                                           GetUserForActivityReporting());
+    } else {
+      activity_storage_->AddActivityPeriod(last_active_check_, now, now,
+                                           GetUserForActivityReporting());
+    }
 
     activity_storage_->PruneActivityPeriods(
         now, max_stored_past_activity_interval_,

chrome/browser/chromeos/policy/device_status_collector_browsertest.cc

@@ -2794,4 +2794,22 @@ TEST_F(ConsumerDeviceStatusCollectorTimeLimitEnabledTest,
   ExpectChildScreenTimeMilliseconds(0.5 * ActivePeriodMilliseconds());
 }
 
+TEST_F(ConsumerDeviceStatusCollectorTimeLimitEnabledTest, ClockChanged) {
+  DeviceStateTransitions test_states[1] = {
+      DeviceStateTransitions::kEnterSessionActive};
+  base::Time initial_time =
+      Time::Now().LocalMidnight() + base::TimeDelta::FromHours(1);
+  status_collector_->SetBaselineTime(initial_time);
+  SimulateStateChanges(test_states, 1);
+
+  // Simulate clock change.
+  status_collector_->SetBaselineTime(initial_time - TimeDelta::FromMinutes(30));
+  test_states[0] = DeviceStateTransitions::kLeaveSessionActive;
+  SimulateStateChanges(test_states, 1);
+
+  GetStatus();
+  ASSERT_EQ(1, device_status_.active_period_size());
+  ExpectChildScreenTimeMilliseconds(ActivePeriodMilliseconds());
+}
+
 }  // namespace policy