Move VoiceEngineObserver into AudioSendStream so that we detect typing noises and return properly in GetStats().

BUG=webrtc:4690

Review URL: https://codereview.webrtc.org/1403363003

Cr-Original-Commit-Position: refs/heads/master@{#10548}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 566ef247b9779f6c9d0e7ec9eea6b037f4682c53
diff --git a/webrtc.gyp b/webrtc.gyp
index c9b3ab5..75ed645 100644
--- a/webrtc.gyp
+++ b/webrtc.gyp
@@ -98,6 +98,7 @@
       'sources': [
         'audio_receive_stream.h',
         'audio_send_stream.h',
+        'audio_state.h',
         'call.h',
         'config.h',
         'frame_callback.h',