arc: Implement safe access to ArcAuthService.

chrome/browser/chromeos/arc/arc_auth_service.cc

Index: chrome/browser/chromeos/arc/arc_auth_service.cc
diff --git a/chrome/browser/chromeos/arc/arc_auth_service.cc b/chrome/browser/chromeos/arc/arc_auth_service.cc
index 2f68cd39a8b671c0e9ea76adffb5520cd2d9f717..71d44e1eb97878a06ba3146d357ca8b3ba490299 100644
--- a/chrome/browser/chromeos/arc/arc_auth_service.cc
+++ b/chrome/browser/chromeos/arc/arc_auth_service.cc
@@ -341,9 +341,6 @@ void ArcAuthService::OnPrimaryUserProfilePrepared(Profile* profile) {
 
   Shutdown();
 
-  profile_ = profile;

[khmel, 2016/07/14 23:17:10]

Actually this incorrect. It was changed while ago (by myself :)). I am fixing
current logic now. There is only ArcHostSupport who uses profile() from
ArcAuthService. I updated ArcHostSupport for safe work.

-  SetState(State::STOPPED);
-
   if (!IsAllowedForProfile(profile))
     return;
 
@@ -353,6 +350,9 @@ void ArcAuthService::OnPrimaryUserProfilePrepared(Profile* profile) {
     return;
   }
 
+  profile_ = profile;
+  SetState(State::STOPPED);
+
   PrefServiceSyncableFromProfile(profile_)->AddSyncedPrefObserver(
       prefs::kArcEnabled, this);
 
@@ -636,6 +636,9 @@ bool ArcAuthService::IsArcManaged() const {
 
 bool ArcAuthService::IsArcEnabled() const {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  if (!IsAllowed())

[khmel, 2016/07/14 23:17:11]

There are several calls to IsArcEnabled without proper call to IsArcAllowed. I
think usage is confusing and it probably makes sense to add extra check
IsAllowed here instead of patching every usage. Logically if arc is not allowed
it is not enabled as well.

[xiyuan, 2016/07/15 17:12:52]

Makes sense.

+    return false;
+
   DCHECK(profile_);
   return profile_->GetPrefs()->GetBoolean(prefs::kArcEnabled);
 }