Reimplement the builtin audio codec factories using the new stuff in api/

webrtc/api/audio_codecs/builtin_audio_decoder_factory.cc

Index: webrtc/api/audio_codecs/builtin_audio_decoder_factory.cc
diff --git a/webrtc/api/audio_codecs/builtin_audio_decoder_factory.cc b/webrtc/api/audio_codecs/builtin_audio_decoder_factory.cc
index 9bd049b0e670b7c7d8708877a5561de4e2b81bc6..69a3e7c533d759a2e595fa8518f248591f694bfa 100644
--- a/webrtc/api/audio_codecs/builtin_audio_decoder_factory.cc
+++ b/webrtc/api/audio_codecs/builtin_audio_decoder_factory.cc
@@ -10,12 +10,70 @@
 
 #include "webrtc/api/audio_codecs/builtin_audio_decoder_factory.h"
 
-#include "webrtc/modules/audio_coding/codecs/builtin_audio_decoder_factory_internal.h"
+#include <memory>
+#include <vector>
+
+#include "webrtc/api/audio_codecs/L16/audio_decoder_L16.h"
+#include "webrtc/api/audio_codecs/audio_decoder_factory_template.h"
+#include "webrtc/api/audio_codecs/g711/audio_decoder_g711.h"
+#if WEBRTC_USE_BUILTIN_G722
+#include "webrtc/api/audio_codecs/g722/audio_decoder_g722.h"  // nogncheck
+#endif
+#if WEBRTC_USE_BUILTIN_ILBC
+#include "webrtc/api/audio_codecs/ilbc/audio_decoder_ilbc.h"  // nogncheck
+#endif
+#if WEBRTC_USE_BUILTIN_ISAC_FIX
+#include "webrtc/api/audio_codecs/isac/audio_decoder_isac_fix.h"  // nogncheck
+#elif WEBRTC_USE_BUILTIN_ISAC_FLOAT
+#include "webrtc/api/audio_codecs/isac/audio_decoder_isac_float.h"  // nogncheck
+#endif
+#if WEBRTC_USE_BUILTIN_OPUS
+#include "webrtc/api/audio_codecs/opus/audio_decoder_opus.h"  // nogncheck
+#endif
 
 namespace webrtc {
 
+namespace {
+
+// Modify an audio decoder to not advertise support for anything.
+template <typename T>
+struct NotAdvertised {
+  using Config = typename T::Config;
+  static rtc::Optional<Config> SdpToConfig(const SdpAudioFormat& audio_format) {
+    return T::SdpToConfig(audio_format);
+  }
+  static void AppendSupportedDecoders(std::vector<AudioCodecSpec>* specs) {
+    // Don't advertise support for anything.
+  }
+  static std::unique_ptr<AudioDecoder> MakeAudioDecoder(const Config& config) {
+    return T::MakeAudioDecoder(config);
+  }
+};
+
+}  // namespace
+
 rtc::scoped_refptr<AudioDecoderFactory> CreateBuiltinAudioDecoderFactory() {
-  return CreateBuiltinAudioDecoderFactoryInternal();
+  return CreateAudioDecoderFactory<
+
+#if WEBRTC_USE_BUILTIN_OPUS
+      AudioDecoderOpus,
+#endif
+
+#if WEBRTC_USE_BUILTIN_ISAC_FIX
+      AudioDecoderIsacFix,
+#elif WEBRTC_USE_BUILTIN_ISAC_FLOAT
+      AudioDecoderIsacFloat,
+#endif
+
+#if WEBRTC_USE_BUILTIN_G722
+      AudioDecoderG722,
+#endif
+
+#if WEBRTC_USE_BUILTIN_ILBC
+      AudioDecoderIlbc,
+#endif
+
+      AudioDecoderG711, NotAdvertised<AudioDecoderL16>>();

[ossu, 2017/08/22 12:29:16]

Neat!

Not advertising L16 in our builtin factory means it won't be used (unless
someone happens to know it's supported and manually mangles the SDP). We should
have a think about what to do about that, but for now we might as well retain
this hidden support for it.

[kwiberg-webrtc, 2017/08/22 12:40:35]

Yes, I realized that this behavior was probably originally a mistake, but I felt
that it was better to keep it even though it's now clearly visible in the code,
and possibly change it in a future CL.

(My tentative plan is in fact to get rid of the Builtin factories, and have all
WebRTC users explicitly list the codecs they want.)

 }
 
 }  // namespace webrtc