Adding TvExtender channel override

The rationale is that the notification importance on TV doesn't
always align with their importance on other devices.
Thus we need the ability to post notification to different
channels just on TV.

Test: ag/1808384
Change-Id: I90a84e3f74d59ca45dac3c6414285bed26482008
diff --git a/core/java/android/app/Notification.java b/core/java/android/app/Notification.java
index 69f4cc0..6033bfa 100644
--- a/core/java/android/app/Notification.java
+++ b/core/java/android/app/Notification.java
@@ -6982,11 +6982,13 @@
         private static final String EXTRA_FLAGS = "flags";
         private static final String EXTRA_CONTENT_INTENT = "content_intent";
         private static final String EXTRA_DELETE_INTENT = "delete_intent";
+        private static final String EXTRA_CHANNEL_ID = "channel_id";
 
         // Flags bitwise-ored to mFlags
         private static final int FLAG_AVAILABLE_ON_TV = 0x1;
 
         private int mFlags;
+        private String mChannelId;
         private PendingIntent mContentIntent;
         private PendingIntent mDeleteIntent;
 
@@ -7007,6 +7009,7 @@
                 null : notif.extras.getBundle(EXTRA_TV_EXTENDER);
             if (bundle != null) {
                 mFlags = bundle.getInt(EXTRA_FLAGS);
+                mChannelId = bundle.getString(EXTRA_CHANNEL_ID);
                 mContentIntent = bundle.getParcelable(EXTRA_CONTENT_INTENT);
                 mDeleteIntent = bundle.getParcelable(EXTRA_DELETE_INTENT);
             }
@@ -7022,6 +7025,7 @@
             Bundle bundle = new Bundle();
 
             bundle.putInt(EXTRA_FLAGS, mFlags);
+            bundle.putString(EXTRA_CHANNEL_ID, mChannelId);
             if (mContentIntent != null) {
                 bundle.putParcelable(EXTRA_CONTENT_INTENT, mContentIntent);
             }
@@ -7043,6 +7047,23 @@
         }
 
         /**
+         * Specifies the channel the notification should be delivered on when shown on TV.
+         * It can be different from the channel that the notification is delivered to when
+         * posting on a non-TV device.
+         */
+        public TvExtender setChannel(String channelId) {
+            mChannelId = channelId;
+            return this;
+        }
+
+        /**
+         * Returns the id of the channel this notification posts to on TV.
+         */
+        public String getChannel() {
+            return mChannelId;
+        }
+
+        /**
          * Supplies a {@link PendingIntent} to be sent when the notification is selected on TV.
          * If provided, it is used instead of the content intent specified
          * at the level of Notification.