Update anroidapp/README for GN build.

webrtc/examples/androidapp/README

Index: webrtc/examples/androidapp/README
diff --git a/webrtc/examples/androidapp/README b/webrtc/examples/androidapp/README
index c8705a8bbaad9d427288a6a69b568381a250c59b..55459c2f3b04e91d5752013d3149a6d348b89950 100644
--- a/webrtc/examples/androidapp/README
+++ b/webrtc/examples/androidapp/README
@@ -1,22 +1,14 @@
 This directory contains an example Android client for https://appr.tc
 
 Prerequisites:
-- "Getting the code" on http://www.webrtc.org/native-code/android
-- Set up webrtc-related GYP variables:
-  export GYP_DEFINES="OS=android $GYP_DEFINES"
-- When targeting both desktop & android, make sure to use a different output_dir
-  value in $GYP_GENERATOR_FLAGS - for example
-  export GYP_GENERATOR_FLAGS="$GYP_GENERATOR_FLAGS output_dir=out_android"
-  or you'll likely end up with mismatched ARM & x86 output artifacts.
-  If you use an output_dir other than out/ make sure to modify the command-lines
-  below appropriately.
-- Finally, run "gclient runhooks" to generate Android-targeting .ninja files.
+- "Getting the code", "Compiling", and "Using the Bundled Android SDK/NDK"
+  on http://www.webrtc.org/native-code/android
 
 Example of building & using the app:
 
 cd <path/to/webrtc>/src
-ninja -C out/Debug AppRTCDemo
-adb install -r out/Debug/apks/AppRTCDemo.apk
+ninja -C out/Default AppRTCDemo
+adb install -r out/Default/apks/AppRTCDemo.apk
 
 In desktop chrome, navigate to https://appr.tc and note the r=<NNN> room
 this redirects to or navigate directly to https://appr.tc/r/<NNN> with