[Android] Implement the native http authentication in xwalk runtime.

  Native http authentication has to be handled in xwalk runtime for Android
port. It is used to provide the xwalk login delegation and handle the http
authentication request. This fix is to provide the native xwalk login delegation
and set up the bridge between the native http authentication handler and corresponding
handler in runtime core java layer.

BUG=https://crosswalk-project.org/jira/browse/XWALK-159
Merge pull request #1135 from ShDavidliu/http_auth

[Android] Implement the native http authentication in xwalk runtime.