title: GoogleAccountCredential.setSelectedAccountName(String) not working on Android 6.0 without Contacts permission
body: <p>I'm retrieving an GoogleAccountCredential object using:</p>
  
  <pre><code>GoogleAccountCredential credential = GoogleAccountCredential.usingOAuth2(
                  context, Arrays.asList({ GmailScopes.MAIL_GOOGLE_COM }))
                  .setBackOff(new ExponentialBackOff())
                  .setSelectedAccountName(email)
  </code></pre>
  
  <p>with email being the Gmail account I'm using on the device.</p>
  
  <p>If I retrieve the account name using credential.getSelectedAccountName the result is null.</p>
  
  <p>This happens only on devices running Android Marshmallow and only if the app does NOT have the Contacts permission. As soon as I grant the Contacts permission everything works.</p>
  
  <p>Why would GoogleAccountCredential.setSelectedAccountName(String) require the Contacts permission? Is it a bug or a feature?</p>