title: CoordinatorLayout ignores margins for views with anchor
body: <p>Given I'm using a layout like this:</p>
  
  <pre><code>&lt;android.support.design.widget.CoordinatorLayout
      android:id="@+id/main_content"
      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"
      android:fitsSystemWindows="true"&gt;
  
      &lt;android.support.design.widget.AppBarLayout
          android:id="@+id/appbar"
          android:layout_width="match_parent"
          android:layout_height="@dimen/flexible_space_image_height"
          android:fitsSystemWindows="true"
          android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"&gt;
  
          &lt;android.support.design.widget.CollapsingToolbarLayout
              android:id="@+id/collapsing_toolbar"
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:fitsSystemWindows="true"
              app:expandedTitleMarginEnd="64dp"
              app:expandedTitleMarginStart="48dp"
              app:statusBarScrim="@android:color/transparent"
              app:layout_scrollFlags="scroll|exitUntilCollapsed"&gt;
  
              &lt;android.support.v7.widget.Toolbar
                  android:id="@+id/toolbar"
                  android:layout_width="match_parent"
                  android:layout_height="?attr/actionBarSize"
                  app:layout_collapseMode="pin"
                  app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
                  /&gt;
  
          &lt;/android.support.design.widget.CollapsingToolbarLayout&gt;
  
      &lt;/android.support.design.widget.AppBarLayout&gt;
  
      &lt;android.support.v7.widget.RecyclerView
          android:id="@+id/mainView"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          app:layout_behavior="@string/appbar_scrolling_view_behavior"
          /&gt;
  
      &lt;android.support.design.widget.FloatingActionButton
          android:layout_width="70dp"
          android:layout_height="70dp"
          android:layout_marginBottom="20dp"
          app:fabSize="normal"
          app:layout_anchor="@id/appbar"
          app:layout_anchorGravity="bottom|center_horizontal"
          /&gt;
  
  &lt;/android.support.design.widget.CoordinatorLayout&gt;
  </code></pre>
  
  <p>Which is pretty much the standard <a href="https://github.com/chrisbanes/cheesesquare" rel="noreferrer">Cheesesquare</a> sample - except the FloatingActionButton, which I would like to move up by about 20dp.</p>
  
  <p>However, this will not work. No matter if I use margin, padding etc - the button will always be centered at the edge of the anchor, like this:</p>
  
  <p><img src="https://i.stack.imgur.com/NOrYO.png" alt="FAB will ignore the margin"></p>
  
  <p>How can I move the FAB up by 20dp as intended?</p>