Android make oval background drawable with chat corner

Create your bubble layout like this

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:layout_margin="16dp"
    android:orientation="vertical">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content" 
        android:text="Hello"
        android:padding="16dp"
        android:background="@drawable/rounded_rect"/>

    <ImageView
        android:layout_marginTop="-1.5dp"
        android:layout_width="8dp"
        android:layout_height="16dp"
        android:layout_gravity="start"
        android:background="@drawable/corner"
        />

</LinearLayout>

Drawable files

rounded_rect.xml

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <solid android:color="#888" />
    <corners
        android:bottomRightRadius="8dp"
        android:topLeftRadius="8dp"
        android:topRightRadius="8dp"/>

</shape>

corner.xml

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <rotate
            android:fromDegrees="45"
            android:pivotX="135%"
            android:pivotY="15%"
            android:toDegrees="45"
            >
            <shape android:shape="rectangle">
                <solid android:color="#888"/>

            </shape>
        </rotate>
    </item>
</layer-list>

This layout will scale with the text you add to the TextView

EDIT

I just now noticed that the arrow in your requirement should be pointing to the left. To get that make some small changes to your bubble layout

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="16dp"
    android:orientation="horizontal">

    <ImageView
        android:layout_width="12dp"
        android:layout_height="12dp"
        android:layout_gravity="bottom"
        android:background="@drawable/corner2"
        />

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Hello"
        android:padding="16dp"
        android:background="@drawable/rounded_rect"/>

</LinearLayout>

corner2.xml

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <rotate
            android:fromDegrees="-45"
            android:pivotX="135%"
            android:pivotY="15%"
            android:toDegrees="45"
            >
            <shape android:shape="rectangle">
                <solid android:color="#888"/>

            </shape>
        </rotate>
    </item>
</layer-list>

OUTPUT