Make an enum class out of NetEqDecoder, and hide the neteq_decoders_ table

webrtc/modules/audio_coding/neteq/neteq_stereo_unittest.cc

Index: webrtc/modules/audio_coding/neteq/neteq_stereo_unittest.cc
diff --git a/webrtc/modules/audio_coding/neteq/neteq_stereo_unittest.cc b/webrtc/modules/audio_coding/neteq/neteq_stereo_unittest.cc
index 5d6f4add4f0d498087626a3c499e6faa22ca4565..66874b8a50cf82f64bbc0640742bb7c83fe9f265 100644
--- a/webrtc/modules/audio_coding/neteq/neteq_stereo_unittest.cc
+++ b/webrtc/modules/audio_coding/neteq/neteq_stereo_unittest.cc
@@ -91,35 +91,35 @@ class NetEqStereoTest : public ::testing::TestWithParam<TestParameters> {
     NetEqDecoder multi_decoder;
     switch (sample_rate_hz_) {
       case 8000:
-        mono_decoder = kDecoderPCM16B;
+        mono_decoder = NetEqDecoder::kDecoderPCM16B;
         if (num_channels_ == 2) {
-          multi_decoder = kDecoderPCM16B_2ch;
+          multi_decoder = NetEqDecoder::kDecoderPCM16B_2ch;
         } else if (num_channels_ == 5) {
-          multi_decoder = kDecoderPCM16B_5ch;
+          multi_decoder = NetEqDecoder::kDecoderPCM16B_5ch;
         } else {
           FAIL() << "Only 2 and 5 channels supported for 8000 Hz.";
         }
         break;
       case 16000:
-        mono_decoder = kDecoderPCM16Bwb;
+        mono_decoder = NetEqDecoder::kDecoderPCM16Bwb;
         if (num_channels_ == 2) {
-          multi_decoder = kDecoderPCM16Bwb_2ch;
+          multi_decoder = NetEqDecoder::kDecoderPCM16Bwb_2ch;
         } else {
           FAIL() << "More than 2 channels is not supported for 16000 Hz.";
         }
         break;
       case 32000:
-        mono_decoder = kDecoderPCM16Bswb32kHz;
+        mono_decoder = NetEqDecoder::kDecoderPCM16Bswb32kHz;
         if (num_channels_ == 2) {
-          multi_decoder = kDecoderPCM16Bswb32kHz_2ch;
+          multi_decoder = NetEqDecoder::kDecoderPCM16Bswb32kHz_2ch;
         } else {
           FAIL() << "More than 2 channels is not supported for 32000 Hz.";
         }
         break;
       case 48000:
-        mono_decoder = kDecoderPCM16Bswb48kHz;
+        mono_decoder = NetEqDecoder::kDecoderPCM16Bswb48kHz;
         if (num_channels_ == 2) {
-          multi_decoder = kDecoderPCM16Bswb48kHz_2ch;
+          multi_decoder = NetEqDecoder::kDecoderPCM16Bswb48kHz_2ch;
         } else {
           FAIL() << "More than 2 channels is not supported for 48000 Hz.";
         }