Add support for swapping feeds in Android AppRTCMobile.

BUG=webrtc:6937

Review-Url: https://codereview.webrtc.org/2682943006
Cr-Commit-Position: refs/heads/master@{#16582}
diff --git a/webrtc/examples/BUILD.gn b/webrtc/examples/BUILD.gn
index 3ee9ae5..59842fc 100644
--- a/webrtc/examples/BUILD.gn
+++ b/webrtc/examples/BUILD.gn
@@ -64,6 +64,8 @@
   }
 
   android_library("AppRTCMobile_javalib") {
+    android_manifest = "androidapp/AndroidManifest.xml"
+
     java_files = [
       "androidapp/src/org/appspot/apprtc/AppRTCAudioManager.java",
       "androidapp/src/org/appspot/apprtc/AppRTCBluetoothManager.java",
@@ -77,7 +79,6 @@
       "androidapp/src/org/appspot/apprtc/DirectRTCClient.java",
       "androidapp/src/org/appspot/apprtc/HudFragment.java",
       "androidapp/src/org/appspot/apprtc/PeerConnectionClient.java",
-      "androidapp/src/org/appspot/apprtc/PercentFrameLayout.java",
       "androidapp/src/org/appspot/apprtc/RoomParametersFetcher.java",
       "androidapp/src/org/appspot/apprtc/SettingsActivity.java",
       "androidapp/src/org/appspot/apprtc/SettingsFragment.java",