Fixing sample-rate dependent band-split filter issues in AEC3

This CL ensures that the number of bands
for the render side matches that for the capture side
when AEC3 is active. Without this, there was problems
when the render rate is different from the capture rate.

BUG=webrtc:6018

Review-Url: https://codereview.webrtc.org/2800033003
Cr-Commit-Position: refs/heads/master@{#17586}
diff --git a/webrtc/modules/audio_processing/audio_processing_impl.cc b/webrtc/modules/audio_processing/audio_processing_impl.cc
index f9cc98f..636d6ca 100644
--- a/webrtc/modules/audio_processing/audio_processing_impl.cc
+++ b/webrtc/modules/audio_processing/audio_processing_impl.cc
@@ -562,11 +562,17 @@
   capture_nonlocked_.capture_processing_format =
       StreamConfig(capture_processing_rate);
 
-  int render_processing_rate = FindNativeProcessRateToUse(
-      std::min(formats_.api_format.reverse_input_stream().sample_rate_hz(),
-               formats_.api_format.reverse_output_stream().sample_rate_hz()),
-      submodule_states_.CaptureMultiBandSubModulesActive() ||
-          submodule_states_.RenderMultiBandSubModulesActive());
+  int render_processing_rate;
+  if (!config_.echo_canceller3.enabled) {
+    render_processing_rate = FindNativeProcessRateToUse(
+        std::min(formats_.api_format.reverse_input_stream().sample_rate_hz(),
+                 formats_.api_format.reverse_output_stream().sample_rate_hz()),
+        submodule_states_.CaptureMultiBandSubModulesActive() ||
+            submodule_states_.RenderMultiBandSubModulesActive());
+  } else {
+    render_processing_rate = capture_processing_rate;
+  }
+
   // TODO(aluebs): Remove this restriction once we figure out why the 3-band
   // splitting filter degrades the AEC performance.
   if (render_processing_rate > kSampleRate32kHz &&
@@ -575,6 +581,7 @@
                                  ? kSampleRate32kHz
                                  : kSampleRate16kHz;
   }
+
   // If the forward sample rate is 8 kHz, the render stream is also processed
   // at this rate.
   if (capture_nonlocked_.capture_processing_format.sample_rate_hz() ==