Stats calls improve APM fuzzer coverage.

A part of the Audio Processing Module interface is GetStatistics. The
call collects stats from submodules. We make sure these calls are made
by the fuzzer to cover that code path.

Bug: webrtc:7820
Change-Id: Ia8f89d9838602dcb2599f676bd5c43e815bbf791
Reviewed-on: https://webrtc-review.googlesource.com/68980
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Commit-Queue: Alex Loiko <aleloi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22817}

test/fuzzers/audio_processing_fuzzer_helper.cc

@@ -114,6 +114,11 @@ void FuzzAudioProcessing(test::FuzzDataHelper* fuzz_data,
       }
     }
 
+    // Make calls to stats gathering functions to cover these
+    // codeways.
+    static_cast<void>(apm->GetStatistics());
+    static_cast<void>(apm->GetStatistics(true));
+
     RTC_DCHECK_NE(apm_return_code, AudioProcessing::kBadDataLengthError);
   }
 }