title: newChooseAccountIntent returns a Name but getToken needs an Email
body: <p>I started with the new Google Play Services and tried to use the information I found in the <a href="http://android-developers.blogspot.de/2012/09/google-play-services-and-oauth-identity.html" rel="nofollow">blog</a> and in the referenced example to create a full working app. IMHO there's something missing in these examples.</p>
  
  <p>The new standard AccountPicker.newChooseAccountIntent can be used to select a Google Account registered on a device. Using that dialog returns the name of the account on return.</p>
  
  <p>Now the examples show how to get a token. The new GoogleAuthUtil.getToken method needs an email to fetch the token.</p>
  
  <p>There's something missing. How can I get the email from a given account name?</p>
  
  <p>Many thanks in advance.</p>
  
  <pre><code>public class MyActivity extends Activity {
  
      public static final String AUTHTOKENSCOPE_DRIVE = "oauth2:https://www.googleapis.com/auth/drive";
  
      String accountName = "";
  
      @Override
      protected void onActivityResult(int requestCode, int resultCode, Intent intent) {
          switch (requestCode) {
              case 1:
                  if (resultCode == RESULT_OK) {
                      accountName = intent.getStringExtra(AccountManager.KEY_ACCOUNT_NAME);
                      // Need to fetch token with email
                      // String token = GoogleAuthUtil.getToken(this, &lt;???email???&gt;,  
                             AUTHTOKENSCOPE_DRIVE);
                  } else {
                  }
  
                  break;
              default:
                  super.onActivityResult(requestCode, resultCode, intent);
          }
      }
  
      @Override
      public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
  
          setContentView(R.layout.activity_main);
  
          int rc = GooglePlayServicesUtil.isGooglePlayServicesAvailable(this);
          switch (rc) {
              case ConnectionResult.SUCCESS:
                  Intent intent = AccountPicker.newChooseAccountIntent(null, null, new String[] {
                          "com.google"
                  },
                          true, null, AUTHTOKENSCOPE_DRIVE, new String[] {
                              "Just a text"
                          }, null);
                  startActivityForResult(intent, 1);
                  break;
          }
      }
  }
  </code></pre>