Split MoveReadPosition into Forward and Backward versions.

webrtc/common_audio/audio_ring_buffer.h

Index: webrtc/common_audio/audio_ring_buffer.h
diff --git a/webrtc/common_audio/audio_ring_buffer.h b/webrtc/common_audio/audio_ring_buffer.h
index 85d2531ad2fcc5af749f3906994fef715b711c06..9d0815a818634f30eee3d8e469bc65a511005ace 100644
--- a/webrtc/common_audio/audio_ring_buffer.h
+++ b/webrtc/common_audio/audio_ring_buffer.h
@@ -38,9 +38,12 @@ class AudioRingBuffer final {
   size_t ReadFramesAvailable() const;
   size_t WriteFramesAvailable() const;
 
-  // Positive values advance the read pointer and negative values withdraw
-  // the read pointer (i.e. flush and stuff the buffer respectively.)
-  void MoveReadPosition(int frames);
+  // Move the read position. The forward version advances the read pointer
+  // towards the write pointer and the backward verison withdraws the read
+  // pointer away from the write pointer (i.e. flush and stuff the buffer
+  // respectively.)
+  void MoveReadPositionForward(size_t frames);
+  void MoveReadPositionBackward(size_t frames);
 
  private:
   // We don't use a ScopedVector because it doesn't support a specialized