[EasyUnlock] Serialize and store BeaconSeeds along as cryptohome key metadata.

chrome/browser/signin/chrome_proximity_auth_client.cc

Index: chrome/browser/signin/chrome_proximity_auth_client.cc
diff --git a/chrome/browser/signin/chrome_proximity_auth_client.cc b/chrome/browser/signin/chrome_proximity_auth_client.cc
index 94e33cfbe5b9a0bbeedc7f31fb6cbedb8a4fb12d..3002689a996127269fa6a81a38c0bcc87dee92da 100644
--- a/chrome/browser/signin/chrome_proximity_auth_client.cc
+++ b/chrome/browser/signin/chrome_proximity_auth_client.cc
@@ -97,7 +97,14 @@ PrefService* ChromeProximityAuthClient::GetPrefService() {
 
 std::unique_ptr<cryptauth::SecureMessageDelegate>
 ChromeProximityAuthClient::CreateSecureMessageDelegate() {
-  return GetCryptAuthService()->CreateSecureMessageDelegate();
+// Note: Although CryptAuthService::CreateSecureMessageDelegate() exists, we
+// don't use it here because the CryptAuthService is not available on the

[Ryan Hansberry, 2017/05/09 02:44:08]

nit: clarify that you "don't use it here *(as opposed to other methods in this
class)* because the CryptAuthService is not available". This was confusing to me
at first.

[Tim Song, 2017/05/10 18:23:26]

Done.

+// ChromeOS login screen.
+#if defined(OS_CHROMEOS)
+  return base::MakeUnique<chromeos::SecureMessageDelegateChromeOS>();
+#else
+  return nullptr;
+#endif
 }
 
 std::unique_ptr<cryptauth::CryptAuthClientFactory>