Merge "Update sample docs for custom default icon"

Author: kroikie

messaging/README.md

@@ -48,6 +48,27 @@ Use Firebase console to send FCM messages to device or emulator.
   message printed in the logs. If it is in the background, a system notification should be
   displayed. When the notification is tapped, the application should return to the quickstart application.
 
+Best Practices
+--------------
+
+## Customize default notification
+
+### Custom default icon
+
+Setting a custom default icon allows you to specify what icon is used for notification
+messages if no icon is set in the notification payload. Also use the custom default
+icon to set the icon used by notification messages sent from the Firebase console.
+If no custom default icon is set and no icon is set in the notification payload,
+the application icon (rendered in white) is used.
+
+### Custom default Color
+
+You can also define what color is used with your notification. Different android
+versions use this settings in different ways: Android < N use this as background color
+for the icon. Android >= N use this to color the icon and the app name.
+
+See the [docs](https://goo.gl/sPggnS) for more.
+
 Result
 -----------
 <img src="app/src/screen.png" height="534" width="300"/>

messaging/app/src/main/AndroidManifest.xml

@@ -8,9 +8,13 @@
         android:label="@string/app_name"
         android:theme="@style/AppTheme">
         <!-- [START fcm_default_icon] -->
+        <!-- Set custom default icon. This is used when no icon is set for incoming notification messages.
+             See README(https://goo.gl/l4GJaQ) for more. -->
         <meta-data
             android:name="com.google.firebase.messaging.default_notification_icon"
             android:resource="@drawable/ic_stat_ic_notification" />
+        <!-- Set color used with incoming notification messages. This is used when no color is set for the incoming
+             notification message. See README(https://goo.gl/6BKBk7) for more. -->
         <meta-data
             android:name="com.google.firebase.messaging.default_notification_color"
             android:resource="@color/colorAccent" />