Закругленный макет вкладки

В TabLayout добавить атрибут app:tabBackground = "@drawable/capsule_sape" это выглядит так

<android.support.design.widget.TabLayout
    android:id = "@+id/tabs"
    app:tabBackground = "@drawable/capsule_sape"
    app:tabGravity = "fill"
    app:tabMode = "scrollable"
    app:tabSelectedTextColor = "@android:color/white"
    android:layout_width = "match_parent"
    android:layout_height = "wrap_content" />

Для Capsule_shape попробуйте код

<?xml version = "1.0" encoding = "utf-8"?>
<shape xmlns:android = "http://schemas.android.com/apk/res/android"
android:shape = "rectangle">
 <corners
  android:bottomLeftRadius = "15dp"
  android:bottomRightRadius = "15dp"
  android:topLeftRadius = "15dp"
  android:topRightRadius = "15dp" />
  <stroke
  android:width = "10dp"
  android:color = "@android:color/transparent"></stroke>
  <solid android:color = "#FFAADD" />
</shape>