[Android] Add test case for onReceivedErrorTest().

This patch is to add test case for onReceivedErrorTest().
Open some urls with error format, the resource client will receive
the related error. Verify the error information with the expected
result.
UNKNOWN is always an error code we should avoid to raise. ERROR_FILE_NOT_FOUND may be more appropriate for this case? I'm not saying change the case now. I just suggest to file a bug to track this thought.