GetProfileFromAccountId() should not return a null point if a valid account id is provided.

chrome/browser/ui/ash/multi_user/multi_user_util.cc

Index: chrome/browser/ui/ash/multi_user/multi_user_util.cc
diff --git a/chrome/browser/ui/ash/multi_user/multi_user_util.cc b/chrome/browser/ui/ash/multi_user/multi_user_util.cc
index f9b4655402afffdf0233e9f03ae972856083c478..3c7c377579ffd0e8271e18434992e5ad1c316777 100644
--- a/chrome/browser/ui/ash/multi_user/multi_user_util.cc
+++ b/chrome/browser/ui/ash/multi_user/multi_user_util.cc
@@ -15,6 +15,7 @@
 #include "google_apis/gaia/gaia_auth_util.h"
 
 #if defined(OS_CHROMEOS)
+#include "chrome/browser/chromeos/profiles/profile_helper.h"
 #include "chrome/browser/ui/ash/multi_user/multi_user_window_manager.h"
 #include "components/user_manager/user_manager.h"
 #endif
@@ -36,7 +37,7 @@ AccountId GetAccountIdFromEmail(const std::string& email) {
 Profile* GetProfileFromAccountId(const AccountId& account_id) {
   // Unit tests can end up here without a |g_browser_process|.
   if (!g_browser_process || !g_browser_process->profile_manager())
-    return NULL;
+    return nullptr;
 
   std::vector<Profile*> profiles =
       g_browser_process->profile_manager()->GetLoadedProfiles();
@@ -46,7 +47,18 @@ Profile* GetProfileFromAccountId(const AccountId& account_id) {
     if (GetAccountIdFromProfile(*profile_iterator) == account_id)
       return *profile_iterator;
   }
-  return NULL;
+
+#if defined(OS_CHROMEOS)
+  // If the refresh token is revoked in the session, GetAccountIdFromProfile()

[Mr4D (OOO till 08-26), 2016/02/16 20:26:18]

Sounds weird. Better:

If in a session the refresh token is revoked, ..

But: what does it exactly mean that the refresh token got revoked? If this is
something where the user has to log out and back log in to get to a running
state, we should possibly enforce an end session since this might otherwise
cause a secure account to be vulnerable.

[Alexander Alekseev, 2016/02/16 20:34:15]

This usually happens when Google account password is changed in another user
session. Sync will not work until re-login. We do not force log out, as network
may be inaccessible.

[xdai1, 2016/02/16 21:36:28]

Done.
Alexander is right about the possibility that the refresh token can be revoked
in a session. Besides, this CL is just some speculation based on the observation
of the crash stack and the observation of the call flow to
AccountTrackerService. It might be one of the reasons that causes the browser
crash, but there might be other reasons too.

I don't think we have knowledge if the refresh token gets revoked or not in this
function, GetProfileByUser() just covers the case that the profile is not
properly returned which is caused by the revoked refresh token that is not
covered by the above for-loop. It's still possible that
GetProfileFromAccountId() receives an invalid account id and thus
GetProfileByUser() returns a null pointer.

+  // returns an empty account id which will cause the profile not being fetched
+  // properly. In this case we fall back to use GetProfileByUser() function.
+  const user_manager::User* user =
+      user_manager::UserManager::Get()->FindUser(account_id);
+  if (user)
+    return chromeos::ProfileHelper::Get()->GetProfileByUser(user);
+#endif
+
+  return nullptr;
 }
 
 Profile* GetProfileFromWindow(aura::Window* window) {