title: CardView in Android doesn't respect constraints from ConstraintLayout
body: <p>I'm trying to place a CardView within a ConstraintLayout, with a specific margin on both sides.</p>
  
  <p>I set the CardView margins compared to parents, both left and right, and then set layout_width at 0dp: it will extend and take all the available space, ignoring the margin.</p>
  
  <p>If instead I put the CardView inside a FrameLayout, and then apply the same exact constraints to the FrameLayout, the FrameLayout will respect them and the CardView will just fit within it (see code below).</p>
  
  <pre><code>&lt;android.support.constraint.ConstraintLayout
      xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      xmlns:tools="http://schemas.android.com/tools"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      tools:context="...MyActivity..."&gt;
      &lt;FrameLayout
          android:layout_width="0dp"
          android:layout_height="0dp"
          android:layout_marginBottom="8dp"
          android:layout_marginEnd="32dp"
          android:layout_marginLeft="32dp"
          android:layout_marginRight="32dp"
          android:layout_marginStart="32dp"
          android:layout_marginTop="32dp"
          app:layout_constraintBottom_toTopOf="@+id/nextButton"
          app:layout_constraintLeft_toLeftOf="parent"
          app:layout_constraintRight_toRightOf="parent"
          app:layout_constraintTop_toTopOf="parent"&gt;
  
          &lt;android.support.v7.widget.CardView&gt;
             &lt;...omitted...&gt;
  </code></pre>
  
  <p>So I got it working the way I need it, but I'd like to understand why CardView doesn't take the margins into account when computing its own width, set at 0dp.</p>