Fix Chromium clang plugin warnings

webrtc/modules/audio_processing/three_band_filter_bank.cc

Index: webrtc/modules/audio_processing/three_band_filter_bank.cc
diff --git a/webrtc/modules/audio_processing/three_band_filter_bank.cc b/webrtc/modules/audio_processing/three_band_filter_bank.cc
index 3e87fe0f3f410617bc49fe7988ebd2813b944386..61071bbff5db6b6119836dbee3b1b05e573774a9 100644
--- a/webrtc/modules/audio_processing/three_band_filter_bank.cc
+++ b/webrtc/modules/audio_processing/three_band_filter_bank.cc
@@ -131,6 +131,8 @@ ThreeBandFilterBank::ThreeBandFilterBank(size_t length)
   }
 }
 
+ThreeBandFilterBank::~ThreeBandFilterBank() = default;
+
 // The analysis can be separated in these steps:
 //   1. Serial to parallel downsampling by a factor of |kNumBands|.
 //   2. Filtering of |kSparsity| different delayed signals with polyphase