title: CardView returns padding for Android API 19, even when i set maxCardElevation 0
body: <p>I have a cardView in my layout</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &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"
      xmlns:card_view="http://schemas.android.com/apk/res-auto"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:background="@color/google_scrim"
      android:fitsSystemWindows="true"
      tools:ignore="Overdraw"&gt;
  
    &lt;android.support.constraint.Guideline
        android:id="@+id/top_guideline"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_begin="0dp"/&gt;
  
    &lt;androidx.cardview.widget.CardView
        android:id="@+id/popover"
        style="@style/popover_style"
        android:layout_width="@dimen/popover_width"
        android:layout_height="0dp"
        android:layout_marginBottom="@dimen/popover_bottom_margin"
        android:layout_marginLeft="@dimen/popover_side_margin"
        android:layout_marginRight="@dimen/popover_side_margin"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHeight_default="wrap"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/popover_top_guideline"
        app:layout_constraintVertical_bias="0"
        card_view:cardCornerRadius="@dimen/popup_corner_radius"
        card_view:cardElevation="0dp"
        card_view:cardMaxElevation="0dp"&gt;
    &lt;/androidx.cardview.widget.CardView&gt;
  &lt;/android.support.constraint.ConstraintLayout&gt;
  </code></pre>
  
  <p>and I see it has different size for Android API above 21 or below it.</p>
  
  <p>I know it's because of the extra padding for shadow created for API below 21, but I cannot make the padding be 0 (like it does when I debug API 21)</p>
  
  <p>I have tried to set cardElevation and macCardElevation to 0 but it didn't help.</p>
  
  <p>Any idea?</p>
  
  <p><a href="https://i.stack.imgur.com/BzpkZ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/BzpkZ.png" alt="enter image description here"></a></p>