arc: Fix situation when ARC cannot be disabled safely.

chrome/browser/chromeos/arc/arc_session_manager.cc

Index: chrome/browser/chromeos/arc/arc_session_manager.cc
diff --git a/chrome/browser/chromeos/arc/arc_session_manager.cc b/chrome/browser/chromeos/arc/arc_session_manager.cc
index 3544f007a7645d368c16cdb8ec58aa1cd3f15a64..b8be63d605e1c76aa26266b3ccb12bd572d3a6b8 100644
--- a/chrome/browser/chromeos/arc/arc_session_manager.cc
+++ b/chrome/browser/chromeos/arc/arc_session_manager.cc
@@ -287,6 +287,12 @@ void ArcSessionManager::OnProvisioningFinished(ProvisioningResult result) {
   // and |State::Active| is not guaranteed to be set here.
   // prefs::kArcDataRemoveRequested also can be active for now.
 
+  if (!IsArcEnabled()) {

[hidehiko, 2017/01/05 08:18:02]

This check does not work in more complicated situation, unfortunately.
E.g.; if "ARC is disabled, then reenabled, and then OnProvisioningFinished is
called", this check passes through.

Could you comment that this check is short-term workaround meanwhile,
and what situation this is trying to address?

[khmel, 2017/01/05 22:55:53]

Done.

+    LOG(WARNING) << " Provisioning result received after Arc was disabled. "

[hidehiko, 2017/01/05 08:18:02]

Please remove a space between '"' and P. Ditto for '"' and I at the line below.

Optional: How about raise the severity to ERROR, considering;
1) This is actually the case we should not hit (although, due to the current
code structure, it is difficult to fix quickly).
2) This should be very rare, IMHO. ("Disabling ARC checkbox manually sounds not
a common user action" multiplies "It needs to be done while provisioning and to
happen the racy situation").

[khmel, 2017/01/05 22:55:53]

The reason of this situation is the same as for line 302. So I would prefer
WARNING here to be consistent. Imho this is not rare case. This happens always
when ARC is disabled while requesting auth code and this is how mojo channel
work. 

+                 << " Ignoring result " << static_cast<int>(result) << ".";
+    return;
+  }
+
   if (provisioning_reported_) {
     // We don't expect ProvisioningResult::SUCCESS is reported twice or reported
     // after an error.