Bug 1477700 Android media notification appears swiped down after video starts r=JanH

Created a dedicated channel for media notifications.

MozReview-Commit-ID: JKFVPNRu2WO

--HG--
extra : rebase_source : f9df42ecae1467c337c0d4bdbd5c5582e47c582c

mobile/android/base/java/org/mozilla/gecko/media/GeckoMediaControlAgent.java

@@ -418,7 +418,7 @@ public class GeckoMediaControlAgent {
 
         if (!AppConstants.Versions.preO) {
             notificationBuilder.setChannelId(NotificationHelper.getInstance(mContext)
-                    .getNotificationChannel(NotificationHelper.Channel.DEFAULT).getId());
+                    .getNotificationChannel(NotificationHelper.Channel.MEDIA).getId());
         }
 
         return notificationBuilder.build();

mobile/android/base/java/org/mozilla/gecko/notifications/NotificationHelper.java

@@ -97,7 +97,11 @@ public final class NotificationHelper implements BundleEventListener {
         /**
          * Mozilla Location Services notification channel.
          */
-        DOWNLOAD
+        DOWNLOAD,
+        /**
+         *  Media notification channel
+         */
+        MEDIA
     }
 
     private final Map<Channel, String> mDefinedNotificationChannels = new HashMap<Channel, String>() {{
@@ -109,6 +113,10 @@ public final class NotificationHelper implements BundleEventListener {
 
         final String DOWNLOAD_NOTIFICATION_TAG = "download-notification-channel";
         put(Channel.DOWNLOAD, DOWNLOAD_NOTIFICATION_TAG);
+
+
+        final String MEDIA_CHANNEL_TAG = "media-notification-channel";
+        put(Channel.MEDIA, MEDIA_CHANNEL_TAG);
     }};
 
     // Holds a list of notifications that should be cleared if the Fennec Activity is shut down.
@@ -176,6 +184,12 @@ public final class NotificationHelper implements BundleEventListener {
                 }
                 break;
 
+                case MEDIA: {
+                    channel = new NotificationChannel(mDefinedNotificationChannels.get(definedChannel),
+                            mContext.getString(R.string.media_notification_channel), NotificationManager.IMPORTANCE_LOW);
+                }
+                break;
+
                 case DEFAULT:
 
                 default: {

mobile/android/base/locales/en-US/android_strings.dtd

@@ -897,4 +897,5 @@ Picture-in-picture mini window -->
 <!-- Notification channels names -->
 <!ENTITY default_notification_channel "&brandShortName;">
 <!ENTITY mls_notification_channel "&vendorShortName; Location Service">
-<!ENTITY download_notification_channel "Downloads">
+<!ENTITY download_notification_channel "Downloads">
+<!ENTITY media_notification_channel "Media playback">

mobile/android/base/strings.xml.in

@@ -650,5 +650,6 @@
 
   <string name="default_notification_channel">&default_notification_channel;</string>
   <string name="mls_notification_channel">&mls_notification_channel;</string>
+  <string name="media_notification_channel">&media_notification_channel;</string>
   <string name="download_notification_channel">&download_notification_channel;</string>
 </resources>