Add missing include guards for audio_ring_buffer.h. Yikes.

webrtc/common_audio/audio_ring_buffer.h

 /*
  *  Copyright (c) 2015 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_AUDIO_RING_BUFFER_H_
+#define WEBRTC_COMMON_AUDIO_AUDIO_RING_BUFFER_H_
 
 #include <stddef.h>
 #include <vector>
 
 struct RingBuffer;
 
 namespace webrtc {
 
 // A ring buffer tailored for float deinterleaved audio. Any operation that
 // cannot be performed as requested will cause a crash (e.g. insufficient data
@@ skipping 20 matching lines @@
   // the read pointer (i.e. flush and stuff the buffer respectively.)
   void MoveReadPosition(int frames);
 
  private:
   // We don't use a ScopedVector because it doesn't support a specialized
   // deleter (like scoped_ptr for instance.)
   std::vector<RingBuffer*> buffers_;
 };
 
 }  // namespace webrtc
+
+#endif  // WEBRTC_COMMON_AUDIO_AUDIO_RING_BUFFER_H_