Make GetConfig() part of the AudioProcessing interface

BUG=chromium:708475
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_chromium_rel_ng

Review-Url: https://codereview.webrtc.org/2802603003
Cr-Commit-Position: refs/heads/master@{#17540}
diff --git a/webrtc/modules/audio_processing/include/audio_processing.h b/webrtc/modules/audio_processing/include/audio_processing.h
index ab924b7..99e4b69 100644
--- a/webrtc/modules/audio_processing/include/audio_processing.h
+++ b/webrtc/modules/audio_processing/include/audio_processing.h
@@ -559,6 +559,11 @@
   virtual NoiseSuppression* noise_suppression() const = 0;
   virtual VoiceDetection* voice_detection() const = 0;
 
+  // Returns the last applied configuration.
+  // TODO(henrik.lundin) Make this method pure virtual when downstream
+  // dependencies have been fixed.
+  virtual AudioProcessing::Config GetConfig() const;
+
   enum Error {
     // Fatal errors.
     kNoError = 0,