[GCM] Be more aggressive about triggering heartbeats when waking from sleep

As long as ten seconds has elapsed since the machine went to sleep, we'll now
force a heartbeat on resume.

BUG=526910

Review URL: https://codereview.chromium.org/1357053003

Cr-Commit-Position: refs/heads/master@{#350226}

google_apis/gcm/engine/heartbeat_manager.cc

@@ -25,6 +25,8 @@ const int kWifiHeartbeatDefaultMs = 1000 * 60 * 15;  // 15 minutes.
 const int kHeartbeatAckDefaultMs = 1000 * 60 * 1;  // 1 minute.
 // Minimum allowed client default heartbeat interval.
 const int kMinClientHeartbeatIntervalMs = 1000 * 60 * 2;  // 2 minutes.
+// Minimum time spent sleeping before we force a new heartbeat.
+const int kMinSuspendTimeMs = 1000 * 10; // 10 seconds.
 
 #if defined(OS_LINUX) && !defined(OS_CHROMEOS)
 // The period at which to check if the heartbeat time has passed. Used to
@@ -118,8 +120,23 @@ void HeartbeatManager::UpdateHeartbeatTimer(scoped_ptr<base::Timer> timer) {
     heartbeat_timer_->Start(FROM_HERE, remaining_delay, timer_task);
 }
 
+void HeartbeatManager::OnSuspend() {
+  // The system is going to sleep. Record the time, so on resume we know how
+  // much time the machine was suspended.
+  suspend_time_ = base::Time::Now();
+}
+
 void HeartbeatManager::OnResume() {
-  CheckForMissedHeartbeat();
+  // The system just resumed from sleep. It's likely that the connection to
+  // MCS was silently lost during that time, even if a heartbeat is not yet
+  // due. Force a heartbeat to detect if the connection is still good.
+  base::TimeDelta elapsed = base::Time::Now() - suspend_time_;
+  UMA_HISTOGRAM_LONG_TIMES("GCM.SuspendTime", elapsed);
+
+  // Make sure a minimum amount of time has passed before forcing a heartbeat to
+  // avoid any tight loop scenarios.
+  if (elapsed > base::TimeDelta::FromMilliseconds(kMinSuspendTimeMs))
+    OnHeartbeatTriggered();
 }
 
 void HeartbeatManager::OnHeartbeatTriggered() {

google_apis/gcm/engine/heartbeat_manager.h

@@ -61,6 +61,7 @@ class GCM_EXPORT HeartbeatManager : public base::PowerObserver {
   void UpdateHeartbeatTimer(scoped_ptr<base::Timer> timer);
 
   // base::PowerObserver override.
+  void OnSuspend() override;
   void OnResume() override;
 
   // Maximum and minimum of the custom client interval that can be requested,
@@ -114,6 +115,9 @@ class GCM_EXPORT HeartbeatManager : public base::PowerObserver {
   // Timer for triggering heartbeats.
   scoped_ptr<base::Timer> heartbeat_timer_;
 
+  // Time at which the machine was last suspended.
+  base::Time suspend_time_;
+
   // Callbacks for interacting with the the connection.
   base::Closure send_heartbeat_callback_;
   ReconnectCallback trigger_reconnect_callback_;

tools/metrics/histograms/histograms.xml

@@ -13616,6 +13616,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="GCM.SuspendTime" units="milliseconds">
+  <owner>zea@chromium.org</owner>
+  <summary>Time elapsed from machine suspend until resume.</summary>
+</histogram>
+
 <histogram name="GCM.UnregistrationCompleteTime" units="milliseconds">
   <owner>jianli@chromium.org</owner>
   <summary>