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

webrtc/modules/audio_coding/neteq/test/neteq_isac_quality_test.cc

Index: webrtc/modules/audio_coding/neteq/test/neteq_isac_quality_test.cc
diff --git a/webrtc/modules/audio_coding/neteq/test/neteq_isac_quality_test.cc b/webrtc/modules/audio_coding/neteq/test/neteq_isac_quality_test.cc
index 4965d0e831cd4bceea438d411ecb792e8799d00d..66b0903f661089aa41c128fb51b0c99faed4289e 100644
--- a/webrtc/modules/audio_coding/neteq/test/neteq_isac_quality_test.cc
+++ b/webrtc/modules/audio_coding/neteq/test/neteq_isac_quality_test.cc
@@ -54,10 +54,9 @@ NetEqIsacQualityTest::NetEqIsacQualityTest()
     : NetEqQualityTest(kIsacBlockDurationMs,
                        kIsacInputSamplingKhz,
                        kIsacOutputSamplingKhz,
-                       kDecoderISAC),
+                       NetEqDecoder::kDecoderISAC),
       isac_encoder_(NULL),
-      bit_rate_kbps_(FLAGS_bit_rate_kbps) {
-}
+      bit_rate_kbps_(FLAGS_bit_rate_kbps) {}
 
 void NetEqIsacQualityTest::SetUp() {
   ASSERT_EQ(1, channels_) << "iSAC supports only mono audio.";