[Auth:Last Credentials Timing] : Introducing API

Storing last successful sign-in/authentication timings, and providing that
information as extra's in updateCredentials and confirmCredentials.
Also, adding a new api: AccountManager#accountAuthenticated(Account).

Change-Id: Icd0dac35b13d61bc28a2e045b96caefffeb353be
diff --git a/core/java/android/accounts/IAccountManager.aidl b/core/java/android/accounts/IAccountManager.aidl
index aa41161..04b3c88 100644
--- a/core/java/android/accounts/IAccountManager.aidl
+++ b/core/java/android/accounts/IAccountManager.aidl
@@ -67,6 +67,7 @@
         boolean expectActivityLaunch);
     void confirmCredentialsAsUser(in IAccountManagerResponse response, in Account account,
         in Bundle options, boolean expectActivityLaunch, int userId);
+    boolean accountAuthenticated(in Account account);
     void getAuthTokenLabel(in IAccountManagerResponse response, String accountType,
         String authTokenType);