I am trying to make 2 views chain horizontally, so they both take `50%` of screen and make their height same as width so they are square. Currently I have this, which doesn't seem to work:

```
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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">

    <View
        android:id="@+id/a"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:background="#F00"
        app:layout_constraintDimensionRatio="H,1:1"
        app:layout_constraintEnd_toStartOf="@+id/b"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <View
        android:id="@+id/b"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:background="#0F0"
        app:layout_constraintDimensionRatio="H,1:1"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@id/a"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

```