Android AppRTCDemo: Add slider for changing camera capture quality during call

webrtc/examples/androidapp/res/layout/fragment_call.xml

 <?xml version="1.0" encoding="utf-8"?>
 
 <RelativeLayout
         xmlns:android="http://schemas.android.com/apk/res/android"
         xmlns:tools="http://schemas.android.com/tools"
         android:layout_width="match_parent"
         android:layout_height="match_parent">
 
     <TextView
         android:id="@+id/contact_name_call"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_centerHorizontal="true"
         android:layout_above="@+id/buttons_call_container"
         android:textSize="24sp"
         android:layout_margin="8dp"/>
 
+    <!-- Note if you change this: the capture quality slider injects itself programmatically below |buttons_call_container|. -->
     <LinearLayout
            android:id="@+id/buttons_call_container"
            android:orientation="horizontal"
            android:layout_alignParentBottom="true"
            android:layout_marginBottom="32dp"
            android:layout_centerHorizontal="true"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content">
 
        <ImageButton
@@ skipping 14 matching lines @@
 
         <ImageButton
            android:id="@+id/button_call_scaling_mode"
            android:background="@drawable/ic_action_return_from_full_screen"
            android:contentDescription="@string/disconnect_call"
            android:layout_width="48dp"
            android:layout_height="48dp"/>
     </LinearLayout>
 
 </RelativeLayout>