[NOT FOR REVIEW] Convert channel counts to size_t.

webrtc/modules/audio_processing/echo_control_mobile_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 32 matching lines @@
   int enable_comfort_noise(bool enable) override;
   bool is_comfort_noise_enabled() const override;
   int SetEchoPath(const void* echo_path, size_t size_bytes) override;
   int GetEchoPath(void* echo_path, size_t size_bytes) const 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;
 
   const AudioProcessing* apm_;
   CriticalSectionWrapper* crit_;
   RoutingMode routing_mode_;
   bool comfort_noise_enabled_;
   unsigned char* external_echo_path_;
 };
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_ECHO_CONTROL_MOBILE_IMPL_H_