title: fitsSystemWindows not working in fragments added by FragmentPagerAdapter
body: <p>My app is working with a FragmentPagerAdapter to add Fragments to the ViewPager. The problem is that the property <code>android:fitsSystemWindows="true"</code> ist not working. It doesn't add padding to the elements.</p>
  
  <p>My main layout looks like following:</p>
  
  <pre><code>&lt;android.support.constraint.ConstraintLayout
      android:layout_width="match_parent"
      android:layout_height="match_parent"&gt;
  
      &lt;android.support.design.widget.TabLayout
          android:id="@+id/viewPagerTab"
          android:layout_width="0dp"
          android:layout_height="48dp"
          app:layout_constraintBottom_toBottomOf="parent"
          app:layout_constraintLeft_toLeftOf="parent"
          app:layout_constraintRight_toRightOf="parent"
          app:tabIndicatorColor="@android:color/transparent"/&gt;
  
      &lt;android.support.v4.view.ViewPager
          android:id="@+id/viewPager"
          android:layout_width="0dp"
          android:layout_height="0dp"
          app:layout_constraintHorizontal_bias="0.0"
          app:layout_constraintLeft_toLeftOf="parent"
          app:layout_constraintRight_toRightOf="parent"
          app:layout_constraintTop_toTopOf="parent"
          app:layout_constraintBottom_toTopOf="@+id/viewPagerTab"/&gt;
  &lt;/android.support.constraint.ConstraintLayout&gt;
  </code></pre>
  
  <p>I set my adapter and add the fragments.</p>
  
  <pre><code>    MainPagerAdapter adapter = new MainPagerAdapter(getSupportFragmentManager());
      adapter.addFragment(new TestFragment(), "Test");
      adapter.addFragment(new GroupFragmentManager(), "Group");
      adapter.addFragment(new ProfileFragment(), "User");
      viewPager.setAdapter(adapter);
  
      viewPagerTab.setupWithViewPager(viewPager);
  </code></pre>
  
  <p>My pager looks like this:</p>
  
  <pre><code>private class MainPagerAdapter extends FragmentPagerAdapter {
      private final List&lt;Fragment&gt; mFragmentList = new ArrayList&lt;&gt;();
      private final List&lt;String&gt; mFragmentTitleList = new ArrayList&lt;&gt;();
  
      public MainPagerAdapter(FragmentManager manager){
          super(manager);
      }
  
      @Override
      public Fragment getItem(int position) {
          return mFragmentList.get(position);
      }
  
      @Override
      public int getCount() {
          return mFragmentList.size();
      }
  
      public void addFragment(Fragment fragment, String title){
          mFragmentList.add(fragment);
          mFragmentTitleList.add(title);
      }
  }
  </code></pre>
  
  <p>The layout of the ProfileFragment just has simple test stuff in it.</p>
  
  <pre><code>&lt;LinearLayout
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:orientation="vertical"
      android:fitsSystemWindows="true"&gt;
      &lt;TextView
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:text="Profile"
          android:fitsSystemWindows="true"/&gt;
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>But it will still not draw a padding.
  I also have set the right styles.</p>
  
  <pre><code>&lt;style name="Base.Theme.SnowLink" parent="Theme.AppCompat.Light.DarkActionBar"&gt;
      &lt;item name="colorPrimary"&gt;@color/colorPrimary&lt;/item&gt;
      &lt;item name="colorPrimaryDark"&gt;@color/colorPrimaryDark&lt;/item&gt;
      &lt;item name="colorAccent"&gt;#FF4081&lt;/item&gt;
      &lt;item name="windowActionBar"&gt;false&lt;/item&gt;
      &lt;item name="windowNoTitle"&gt;true&lt;/item&gt;
  
      &lt;item name="android:windowTranslucentStatus"&gt;true&lt;/item&gt;
      &lt;item name="android:windowTranslucentNavigation"&gt;true&lt;/item&gt;
  &lt;/style&gt;
  </code></pre>
  
  <p>I searched and tested a lot. I think android has some problems with the loaded fragments, because it works in the activity layout. I also use databinding.</p>
  
  <p>Thanks in advance!</p>