Enable Android APK trybots by default.

As the new bots building the WebRTC native tests for Android as APKs
and executing them on a device has now proven to be reasonably stable,
it is time to enable them by default for tryjobs.

TEST=several green builds sent from a WebRTC checkout.
BUG=chromium:312827
R=tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/7529004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5440 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 9d69b6f..c7f3cc5 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -160,6 +160,8 @@
 
   android_bots = [
       'android',
+      'android_apk',
+      'android_apk_rel',
       'android_rel',
       'android_clang',
   ]