Update last audio tick time during suspend and resume.

If someone suspends their computer and resumes more than a minute
later, the browser io thread may tick before the audio thread can
update the last tick time ==> crash :(

The solution is to disable hang detection during suspend and only
reenable it once resume completes; at which point we can update
the tick count. If we're actually hung, we'll crash after the next
interval elapses.

BUG=471046
TEST=none

Review URL: https://codereview.chromium.org/1036933003

Cr-Commit-Position: refs/heads/master@{#322509}

media/audio/audio_manager.cc

@@ -9,6 +9,7 @@
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
+#include "base/power_monitor/power_monitor.h"
 #include "build/build_config.h"
 #include "media/audio/fake_audio_log_factory.h"
 
@@ -19,24 +20,46 @@ AudioManager* g_last_created = NULL;
 // Helper class for managing global AudioManager data and hang timers. If the
 // audio thread is unresponsive for more than a minute we want to crash the
 // process so we can catch offenders quickly in the field.
-class AudioManagerHelper {
+class AudioManagerHelper : public base::PowerObserver {
  public:
-  AudioManagerHelper() : max_hung_task_time_(base::TimeDelta::FromMinutes(1)) {}
-  ~AudioManagerHelper() {}
+  AudioManagerHelper()
+      : max_hung_task_time_(base::TimeDelta::FromMinutes(1)),
+        hang_detection_enabled_(true) {}
+  ~AudioManagerHelper() override {}
 
   void StartHangTimer(
       const scoped_refptr<base::SingleThreadTaskRunner>& monitor_task_runner) {
     CHECK(!monitor_task_runner_);
     monitor_task_runner_ = monitor_task_runner;
+    base::PowerMonitor::Get()->AddObserver(this);
     UpdateLastAudioThreadTimeTick();
     CrashOnAudioThreadHang();
   }
 
+  // Disable hang detection when the system goes into the suspend state.
+  void OnSuspend() override {
+    base::AutoLock lock(hang_lock_);
+    hang_detection_enabled_ = false;
+  }
+
+  // Reenable hang detection once the system comes out of the suspend state.
+  void OnResume() override {
+    base::AutoLock lock(hang_lock_);
+    hang_detection_enabled_ = true;
+    last_audio_thread_timer_tick_ = base::TimeTicks::Now();
+  }
+
   // Runs on |monitor_task_runner| typically, but may be started on any thread.
   void CrashOnAudioThreadHang() {
     base::AutoLock lock(hang_lock_);
-    CHECK(base::TimeTicks::Now() - last_audio_thread_timer_tick_ <=
-          max_hung_task_time_);
+
+    // Don't attempt to verify the tick time if the system is in the process of
+    // suspending or resuming.
+    if (hang_detection_enabled_) {
+      CHECK(base::TimeTicks::Now() - last_audio_thread_timer_tick_ <=
+            max_hung_task_time_);
+    }
+
     monitor_task_runner_->PostDelayedTask(
         FROM_HERE, base::Bind(&AudioManagerHelper::CrashOnAudioThreadHang,
                               base::Unretained(this)),
@@ -63,6 +86,7 @@ class AudioManagerHelper {
   scoped_refptr<base::SingleThreadTaskRunner> monitor_task_runner_;
 
   base::Lock hang_lock_;
+  bool hang_detection_enabled_;
   base::TimeTicks last_audio_thread_timer_tick_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioManagerHelper);