Move smoothing filter to common audio and exp_filter to base/analytics.

An earlier attempt of this work can be found here https://codereview.webrtc.org/2520003005/#ps100001, but was reverted.

PS4 in that CL was not valid since separation of BUILD.gn can cause internal bot to fail.

This is a new attempt, which is the same as https://codereview.webrtc.org/2520003005/#ps100001 but PS4 reverted.

BUG=webrtc:6443
TBR=tommi@webrtc.org, solenberg@webrtc.org

Review-Url: https://codereview.webrtc.org/2532523002
Cr-Commit-Position: refs/heads/master@{#15233}
diff --git a/webrtc/modules/audio_coding/BUILD.gn b/webrtc/modules/audio_coding/BUILD.gn
index 0e78abf..8c5a079 100644
--- a/webrtc/modules/audio_coding/BUILD.gn
+++ b/webrtc/modules/audio_coding/BUILD.gn
@@ -708,6 +708,7 @@
     ":audio_decoder_interface",
     ":audio_encoder_interface",
     ":audio_network_adaptor",
+    "../../base:rtc_analytics",
     "../../base:rtc_base_approved",
   ]
 
@@ -764,8 +765,6 @@
     "audio_network_adaptor/frame_length_controller.cc",
     "audio_network_adaptor/frame_length_controller.h",
     "audio_network_adaptor/include/audio_network_adaptor.h",
-    "audio_network_adaptor/smoothing_filter.cc",
-    "audio_network_adaptor/smoothing_filter.h",
   ]
 
   deps = [