[NOT FOR REVIEW] Convert channel counts to size_t.

webrtc/modules/audio_processing/level_estimator_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 24 matching lines @@
  private:
   // LevelEstimator implementation.
   int Enable(bool enable) override;
   int RMS() override;
 
   // ProcessingComponent implementation.
   void* CreateHandle() const override;
   int InitializeHandle(void* handle) const override;
   int ConfigureHandle(void* handle) const override;
   void DestroyHandle(void* handle) const override;
-  int num_handles_required() const override;
+  size_t num_handles_required() const override;
   int GetHandleError(void* handle) const override;
 
   CriticalSectionWrapper* crit_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_LEVEL_ESTIMATOR_IMPL_H_