Fix Chromium clang plugin warnings

BUG=webrtc:163

Review-Url: https://codereview.webrtc.org/2288593004
Cr-Commit-Position: refs/heads/master@{#13961}
diff --git a/webrtc/modules/audio_processing/test/test_utils.cc b/webrtc/modules/audio_processing/test/test_utils.cc
index 0d50b0c..95490f0 100644
--- a/webrtc/modules/audio_processing/test/test_utils.cc
+++ b/webrtc/modules/audio_processing/test/test_utils.cc
@@ -36,6 +36,8 @@
 ChannelBufferWavReader::ChannelBufferWavReader(std::unique_ptr<WavReader> file)
     : file_(std::move(file)) {}
 
+ChannelBufferWavReader::~ChannelBufferWavReader() = default;
+
 bool ChannelBufferWavReader::Read(ChannelBuffer<float>* buffer) {
   RTC_CHECK_EQ(file_->num_channels(), buffer->num_channels());
   interleaved_.resize(buffer->size());
@@ -53,6 +55,8 @@
 ChannelBufferWavWriter::ChannelBufferWavWriter(std::unique_ptr<WavWriter> file)
     : file_(std::move(file)) {}
 
+ChannelBufferWavWriter::~ChannelBufferWavWriter() = default;
+
 void ChannelBufferWavWriter::Write(const ChannelBuffer<float>& buffer) {
   RTC_CHECK_EQ(file_->num_channels(), buffer.num_channels());
   interleaved_.resize(buffer.size());