Fix fuzzer-found bug in fuzzer

The fuzzer itself does not call the APM API correctly.

Bug: chromium:1028614
Change-Id: If94808e6d3a1f550c1001b081321e87448e4be49
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/160703
Reviewed-by: Alessio Bazzica <alessiob@webrtc.org>
Commit-Queue: Sam Zackrisson <saza@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29922}
diff --git a/test/fuzzers/audio_processing_fuzzer_helper.cc b/test/fuzzers/audio_processing_fuzzer_helper.cc
index eb2e0e8..87b68f4 100644
--- a/test/fuzzers/audio_processing_fuzzer_helper.cc
+++ b/test/fuzzers/audio_processing_fuzzer_helper.cc
@@ -122,8 +122,8 @@
             StreamConfig(output_rate, num_channels), ptr_to_float_frames);
       } else {
         apm_return_code = apm->ProcessReverseStream(
-            ptr_to_float_frames, StreamConfig(input_rate, 1),
-            StreamConfig(output_rate, 1), ptr_to_float_frames);
+            ptr_to_float_frames, StreamConfig(input_rate, num_channels),
+            StreamConfig(output_rate, num_channels), ptr_to_float_frames);
       }
     } else {
       const int num_channels = fuzz_data->ReadOrDefaultValue(true) ? 2 : 1;