title: Cancel task in auth case
body: <p>I have created task for creating user, and then I want to cancel the task or remove listener. How can I do it ?</p>
  
  <pre><code> Task authTask = mAuth.createUserWithEmailAndPassword(emailEditText.toString(), passwordEditText.toString()).addOnSuccessListener(new OnSuccessListener&lt;AuthResult&gt;() {
          @Override
          public void onSuccess(AuthResult authResult) {
              //todo
          }
      });
  </code></pre>
  
  <p>com.google.android.gms.tasks.Task doesn't have api for it. 
  Why ? </p>