Update common_audio

Corresponds to upstream commit 524e9b043e7e86fd72353b987c9d5f6a1ebf83e1

Update notes:

 * Moved src/ to webrtc/ to easily diff against the third_party/webrtc
   in the chromium tree

 * ARM/NEON/MIPS support is not yet hooked up

 * Tests have not been copied

webrtc/common_audio/vad/include/vad.h

@@ -0,0 +1,50 @@
+/*
+ *  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_COMMON_AUDIO_VAD_INCLUDE_VAD_H_
+#define WEBRTC_COMMON_AUDIO_VAD_INCLUDE_VAD_H_
+
+#include "webrtc/base/checks.h"
+#include "webrtc/base/scoped_ptr.h"
+#include "webrtc/common_audio/vad/include/webrtc_vad.h"
+#include "webrtc/typedefs.h"
+
+namespace webrtc {
+
+class Vad {
+ public:
+  enum Aggressiveness {
+    kVadNormal = 0,
+    kVadLowBitrate = 1,
+    kVadAggressive = 2,
+    kVadVeryAggressive = 3
+  };
+
+  enum Activity { kPassive = 0, kActive = 1, kError = -1 };
+
+  virtual ~Vad() = default;
+
+  // Calculates a VAD decision for the given audio frame. Valid sample rates
+  // are 8000, 16000, and 32000 Hz; the number of samples must be such that the
+  // frame is 10, 20, or 30 ms long.
+  virtual Activity VoiceActivity(const int16_t* audio,
+                                 size_t num_samples,
+                                 int sample_rate_hz) = 0;
+
+  // Resets VAD state.
+  virtual void Reset() = 0;
+};
+
+// Returns a Vad instance that's implemented on top of WebRtcVad.
+rtc::scoped_ptr<Vad> CreateVad(Vad::Aggressiveness aggressiveness);
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_COMMON_AUDIO_VAD_INCLUDE_VAD_H_