Fix Chromium clang plugin warnings

webrtc/modules/audio_processing/echo_cancellation_impl.h

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 10 matching lines @@
 #include "webrtc/modules/audio_processing/render_queue_item_verifier.h"
 
 namespace webrtc {
 
 class AudioBuffer;
 
 class EchoCancellationImpl : public EchoCancellation {
  public:
   EchoCancellationImpl(rtc::CriticalSection* crit_render,
                        rtc::CriticalSection* crit_capture);
-  virtual ~EchoCancellationImpl();
+  ~EchoCancellationImpl() override;
 
   int ProcessRenderAudio(const AudioBuffer* audio);
   int ProcessCaptureAudio(AudioBuffer* audio, int stream_delay_ms);
 
   // EchoCancellation implementation.
   bool is_enabled() const override;
   int stream_drift_samples() const override;
   SuppressionLevel suppression_level() const override;
   bool is_drift_compensation_enabled() const override;
 
@@ skipping 74 matching lines @@
 
   std::vector<std::unique_ptr<Canceller>> cancellers_;
   std::unique_ptr<StreamProperties> stream_properties_;
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(EchoCancellationImpl);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_ECHO_CANCELLATION_IMPL_H_