@Override
 protected boolean handleBackPressed() {
   if (mTab == null) return false;
   if (mTab.canGoBack()) {
     mTab.goBack();
     return true;
   }
   return false;
 }
  @Override
  public void finishNativeInitialization() {
    mTab =
        FullScreenActivityTab.create(
            this, getWindowAndroid(), getActivityDirectory(), getSavedInstanceState(), this);
    getTabModelSelector().setTab(mTab);
    mTab.show(TabSelectionType.FROM_NEW);

    ControlContainer controlContainer = (ControlContainer) findViewById(R.id.control_container);
    initializeCompositorContent(
        new LayoutManagerDocument(getCompositorViewHolder()),
        (View) controlContainer,
        (ViewGroup) findViewById(android.R.id.content),
        controlContainer);

    getActivityTab().setFullscreenManager(getFullscreenManager());
    super.finishNativeInitialization();
  }