Move android audio device code into sdk/android

This CL adds a stand-alone Android AudioDeviceModule in the
sdk/android folder. It's forked from modules/audio_device/android/
and then simplified for the Android case. The stand-alone Android
ADM is available both in the native_api and also under a field trial
in the Java API.

Bug: webrtc:7452
Change-Id: If6e558026bd0ccb52f56d78ac833339a5789d300
Reviewed-on: https://webrtc-review.googlesource.com/60541
Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22517}
diff --git a/sdk/android/native_api/DEPS b/sdk/android/native_api/DEPS
new file mode 100644
index 0000000..020e1cb
--- /dev/null
+++ b/sdk/android/native_api/DEPS
@@ -0,0 +1,4 @@
+include_rules = [
+  "+modules/audio_device/include/audio_device.h",
+  "+system_wrappers/include",
+]