title: Toolbar not collapsing on scroll in CoordinatorLayout
body: <p>I am using the following layout file to implement a coordinator layout with collapsing toolbar (when the user scrolls down, it should collapse, and reappear when they scroll up) However, this scroll off screen/collapse functionality is not working, and I don't know why. Instead of reacting, the toolbar, and tab bar stay statically at the top of the screen.</p>
  
  <pre><code>&lt;android.support.design.widget.CoordinatorLayout
      xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      android:layout_width="match_parent"
      android:layout_height="match_parent"&gt;
  
      &lt;ScrollView
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          app:layout_behavior="@string/appbar_scrolling_view_behavior"&gt;
          &lt;!--                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ --&gt;
          &lt;LinearLayout
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:orientation="vertical" &gt;
  
              &lt;Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Alpha" /&gt;
              &lt;Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Beta" /&gt;
              &lt;!-- a bunch of content just to make the view long enough to scroll --&gt;
              &lt;Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Upsilon" /&gt;
  
          &lt;/LinearLayout&gt;
  
      &lt;/ScrollView&gt;
  
  
      &lt;android.support.design.widget.AppBarLayout
          android:layout_width="match_parent"
          android:layout_height="wrap_content" &gt;
  
          &lt;android.support.v7.widget.Toolbar
              android:id="@+id/toolbar"
              android:layout_width="match_parent"
              android:layout_height="?attr/actionBarSize"
              android:background="?attr/colorAccent"
              app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
              app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
              app:layout_scrollFlags="scroll|enterAlways" /&gt;
              &lt;!--                    ^^^^^^^^^^^^^^^^^^ --&gt;
  
          &lt;android.support.design.widget.TabLayout
              android:id="@+id/tabs"
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              app:layout_scrollFlags="scroll|enterAlways" /&gt;
              &lt;!--                    ^^^^^^^^^^^^^^^^^^ --&gt;
  
      &lt;/android.support.design.widget.AppBarLayout&gt;
  
      &lt;android.support.design.widget.FloatingActionButton
          android:id="@+id/fab"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_gravity="bottom|end"
          android:layout_margin="@dimen/fab_padding"
          android:src="@drawable/ic_add"/&gt;
  
  &lt;/android.support.design.widget.CoordinatorLayout&gt;
  </code></pre>
  
  <p>Any help? Thanks!</p>