Use GoogleAuthUtil's getToken instead of AccountManager

sync/android/java/src/org/chromium/sync/signin/AccountManagerDelegate.java

Index: sync/android/java/src/org/chromium/sync/signin/AccountManagerDelegate.java
diff --git a/sync/android/java/src/org/chromium/sync/signin/AccountManagerDelegate.java b/sync/android/java/src/org/chromium/sync/signin/AccountManagerDelegate.java
index cef541efe81bb7838c94cffa788e6520e6c111b2..eafc4ae8202ef7e62d700a60987366426a14cccd 100644
--- a/sync/android/java/src/org/chromium/sync/signin/AccountManagerDelegate.java
+++ b/sync/android/java/src/org/chromium/sync/signin/AccountManagerDelegate.java
@@ -5,11 +5,7 @@
 package org.chromium.sync.signin;
 
 import android.accounts.Account;
-import android.accounts.AccountManagerCallback;
-import android.accounts.AccountManagerFuture;
 import android.accounts.AuthenticatorDescription;
-import android.os.Bundle;
-import android.os.Handler;
 
 import org.chromium.base.Callback;
 
@@ -24,14 +20,34 @@ public interface AccountManagerDelegate {
      */
     Account[] getAccountsByType(String type);
 
+    /**
+     * Get all the accounts for a given {@code type}.
+     */
     void getAccountsByType(String type, Callback<Account[]> callback);
 
-    AccountManagerFuture<Bundle> getAuthToken(Account account, String authTokenType,
-            boolean notifyAuthFailure, AccountManagerCallback<Bundle> callback, Handler handler);
+    /**
+     * @param account The {@link Account} for which the auth token is requested.
+     * @param authTokenScope The scope of the authToken being requested.
+     * @return The auth token fetched from the authenticator.
+     * The authenticator can throw an {@link AuthException} to indicate a failure in fetching the
+     * auth token perhaps due to a transient error or when user intervention is required (like
+     * confirming the credentials) which is expressed as an {@link Intent} to the handler.
+     * This should only be called on a background thread.
+     */
+    String getAuthToken(Account account, String authTokenScope) throws AuthException;
 
+    /**
+     * Invalidate the {@code authToken} associated with account type {@code accountType}.
+     */
     void invalidateAuthToken(String accountType, String authToken);
 
+    /**
+     * Get all the available authenticator types.
+     */
     AuthenticatorDescription[] getAuthenticatorTypes();
 
+    /**
+     * Check whether the {@code account} has all the features listed in {@code features}.
+     */
     void hasFeatures(Account account, String[] features, Callback<Boolean> callback);
 }