Remove legacy EchoControlFactory::Create

Bug: webrtc:10913
Change-Id: I34af9abe76f5b08d7dc5c3e0281fafc14a71eed8
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/159031
Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org>
Reviewed-by: Per Ã…hgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29741}
diff --git a/modules/audio_processing/audio_processing_impl.cc b/modules/audio_processing/audio_processing_impl.cc
index abfcc05..9a0ce88 100644
--- a/modules/audio_processing/audio_processing_impl.cc
+++ b/modules/audio_processing/audio_processing_impl.cc
@@ -1783,6 +1783,7 @@
     if (echo_control_factory_) {
       submodules_.echo_controller = echo_control_factory_->Create(
           proc_sample_rate_hz(), num_reverse_channels(), num_proc_channels());
+      RTC_DCHECK(submodules_.echo_controller);
     } else {
       submodules_.echo_controller = std::make_unique<EchoCanceller3>(
           EchoCanceller3Config(), proc_sample_rate_hz(), num_reverse_channels(),