chromeos: Avoid crash on synchronous suspend readiness call.

chromeos/dbus/power_manager_client.cc

Index: chromeos/dbus/power_manager_client.cc
diff --git a/chromeos/dbus/power_manager_client.cc b/chromeos/dbus/power_manager_client.cc
index 0d707e266db358812d22842c43997e3e785e6db6..3186f2ffefca09a4749dba19119694d173ae4b7e 100644
--- a/chromeos/dbus/power_manager_client.cc
+++ b/chromeos/dbus/power_manager_client.cc
@@ -59,6 +59,7 @@ class PowerManagerClientImpl : public PowerManagerClient {
         suspend_is_pending_(false),
         suspending_from_dark_resume_(false),
         num_pending_suspend_readiness_callbacks_(0),
+        notifying_observers_about_suspend_imminent_(false),
         last_is_projecting_(false),
         weak_ptr_factory_(this) {}
 
@@ -548,10 +549,17 @@ class PowerManagerClientImpl : public PowerManagerClient {
     suspending_from_dark_resume_ = in_dark_resume;
     num_pending_suspend_readiness_callbacks_ = 0;
 
+    // Record the fact that observers are being notified to ensure that we don't
+    // report readiness prematurely if one of them calls
+    // GetSuspendReadinessCallback() and then runs the callback synchonously
+    // instead of asynchronously.
+    notifying_observers_about_suspend_imminent_ = true;
     if (suspending_from_dark_resume_)
       FOR_EACH_OBSERVER(Observer, observers_, DarkSuspendImminent());
     else
       FOR_EACH_OBSERVER(Observer, observers_, SuspendImminent());
+    notifying_observers_about_suspend_imminent_ = false;
+
     base::PowerMonitorDeviceSource::HandleSystemSuspending();
     MaybeReportSuspendReadiness();
   }
@@ -748,6 +756,11 @@ class PowerManagerClientImpl : public PowerManagerClient {
   void MaybeReportSuspendReadiness() {
     CHECK(suspend_is_pending_);
 
+    // Avoid reporting suspend readiness if some observers have yet to be
+    // notified about the pending attempt.
+    if (notifying_observers_about_suspend_imminent_)
+      return;
+
     if (num_pending_suspend_readiness_callbacks_ > 0) {
       // TODO(derat): Remove after http://crbug.com/648580 is fixed.
       VLOG(1) << "Not reporting suspend readiness; waiting for "
@@ -833,6 +846,11 @@ class PowerManagerClientImpl : public PowerManagerClient {
   // attempt but have not yet been called.
   int num_pending_suspend_readiness_callbacks_;
 
+  // Inspected by MaybeReportSuspendReadiness() to avoid prematurely notifying
+  // powerd about suspend readiness while |observers_|' SuspendImminent()
+  // methods are being called by HandleSuspendImminent().
+  bool notifying_observers_about_suspend_imminent_;
+
   // Last state passed to SetIsProjecting().
   bool last_is_projecting_;