Surface ResidualEchoDetector creation to API

This allows users to inject the residual echo detector, as a step toward making it an optional part of compilation.

Bug: webrtc:11292, webrtc:11539
Change-Id: I7fcc8dbaced67a82851cd6cdcbc115eb01c21fcf
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/174040
Reviewed-by: Per Ã…hgren <peah@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Sam Zackrisson <saza@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31222}
diff --git a/api/DEPS b/api/DEPS
index 1e92b12..1212b43 100644
--- a/api/DEPS
+++ b/api/DEPS
@@ -246,6 +246,10 @@
     "+modules/audio_processing/include/audio_processing.h",
   ],
 
+  "echo_detector_creator\.h": [
+    "+modules/audio_processing/include/audio_processing.h",
+  ],
+
   "fake_frame_decryptor\.h": [
     "+rtc_base/ref_counted_object.h",
   ],