Reducing neteq sync buffer size.

BUG=608644

Review-Url: https://codereview.webrtc.org/1947453002
Cr-Commit-Position: refs/heads/master@{#12614}
diff --git a/webrtc/modules/audio_coding/neteq/neteq_impl.h b/webrtc/modules/audio_coding/neteq/neteq_impl.h
index 2203de1..2be3ee4 100644
--- a/webrtc/modules/audio_coding/neteq/neteq_impl.h
+++ b/webrtc/modules/audio_coding/neteq/neteq_impl.h
@@ -210,7 +210,9 @@
   static const int kOutputSizeMs = 10;
   static const size_t kMaxFrameSize = 5760;  // 120 ms @ 48 kHz.
   // TODO(hlundin): Provide a better value for kSyncBufferSize.
-  static const size_t kSyncBufferSize = 2 * kMaxFrameSize;
+  // Current value is kMaxFrameSize + 60 ms * 48 kHz, which is enough for
+  // calculating correlations of current frame against history.
+  static const size_t kSyncBufferSize = kMaxFrameSize + 60 * 48;
 
   // Inserts a new packet into NetEq. This is used by the InsertPacket method
   // above. Returns 0 on success, otherwise an error code.