Hide ACMCodecDB::database_ behind accessors

webrtc/modules/audio_coding/main/acm2/acm_codec_database.cc

Index: webrtc/modules/audio_coding/main/acm2/acm_codec_database.cc
diff --git a/webrtc/modules/audio_coding/main/acm2/acm_codec_database.cc b/webrtc/modules/audio_coding/main/acm2/acm_codec_database.cc
index f7842ce5b174dcb279c2dac07d98063eff2050b1..59bb233eef92cb77976471bff7b83f23a6c8a3f9 100644
--- a/webrtc/modules/audio_coding/main/acm2/acm_codec_database.cc
+++ b/webrtc/modules/audio_coding/main/acm2/acm_codec_database.cc
@@ -29,11 +29,6 @@ namespace acm2 {
 
 namespace {
 
-// Checks if the bitrate is valid for the codec.
-bool IsRateValid(int codec_id, int rate) {
-  return ACMCodecDB::database_[codec_id].rate == rate;
-}
-
 // Checks if the bitrate is valid for iSAC.
 bool IsISACRateValid(int rate) {
   return (rate == -1) || ((rate <= 56000) && (rate >= 10000));
@@ -298,8 +293,7 @@ int ACMCodecDB::CodecNumber(const CodecInst& codec_inst) {
         ? codec_id : kInvalidRate;
   }
 
-  return IsRateValid(codec_id, codec_inst.rate) ?
-      codec_id : kInvalidRate;
+  return database_[codec_id].rate == codec_inst.rate ? codec_id : kInvalidRate;
 }
 
 // Looks for a matching payload name, frequency, and channels in the