Added namespaces in the newly C++ified AEC code

webrtc/modules/audio_processing/aec/aec_common.h

 /*
  *  Copyright (c) 2014 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.
  */
 
 #ifndef WEBRTC_MODULES_AUDIO_PROCESSING_AEC_AEC_COMMON_H_
 #define WEBRTC_MODULES_AUDIO_PROCESSING_AEC_AEC_COMMON_H_
 
 #include "webrtc/typedefs.h"
 
 #ifdef _MSC_VER /* visual c++ */
 #define ALIGN16_BEG __declspec(align(16))
 #define ALIGN16_END
 #else /* gcc or icc */
 #define ALIGN16_BEG
 #define ALIGN16_END __attribute__((aligned(16)))
 #endif
 
+#ifdef __cplusplus
+namespace webrtc {
+#endif
+
 extern ALIGN16_BEG const float ALIGN16_END WebRtcAec_sqrtHanning[65];
 extern ALIGN16_BEG const float ALIGN16_END WebRtcAec_weightCurve[65];
 extern ALIGN16_BEG const float ALIGN16_END WebRtcAec_overDriveCurve[65];
 extern const float WebRtcAec_kExtendedSmoothingCoefficients[2][2];
 extern const float WebRtcAec_kNormalSmoothingCoefficients[2][2];
 extern const float WebRtcAec_kMinFarendPSD;
 
+#ifdef __cplusplus
+}  // namespace webrtc
+#endif
+
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_AEC_AEC_COMMON_H_