LeanbackDemo: Bring piped activity to full-screen when relaunched

Bug: 26696836
Change-Id: Ic0e682d79eaa76b8e53b9a7c58c667fe22d3ab42
diff --git a/samples/SupportLeanbackDemos/AndroidManifest.xml b/samples/SupportLeanbackDemos/AndroidManifest.xml
index 1ea6a56..d02eefe 100644
--- a/samples/SupportLeanbackDemos/AndroidManifest.xml
+++ b/samples/SupportLeanbackDemos/AndroidManifest.xml
@@ -62,6 +62,7 @@
                 "screenSize|smallestScreenSize|screenLayout|orientation"
             android:resizeableActivity="true"
             android:supportsPictureInPicture="true"
+            android:launchMode="singleTask"
             android:exported="true" />
 
         <activity android:name="PlaybackOverlaySupportActivity"
@@ -69,6 +70,7 @@
                 "screenSize|smallestScreenSize|screenLayout|orientation"
             android:resizeableActivity="true"
             android:supportsPictureInPicture="true"
+            android:launchMode="singleTask"
             android:exported="true" />
 
         <activity android:name="VerticalGridActivity"