Revert of AcmReceiver::DecoderByPayloadType: Ask NetEq for decoder (patchset #1 id:1 of https://codereview.webrtc.org/2341283002/ )

Reason for revert:
Seems to have broken Chromium tests.

Original issue's description:
> AcmReceiver::DecoderByPayloadType: Ask NetEq for decoder
>
> Instead of looking in AcmReceiver::decoders_, which we're trying to
> get rid of.
>
> BUG=webrtc:5801
>
> Committed: https://crrev.com/07772e4738ef8007280f97a0245eef34b9ca9391
> Cr-Commit-Position: refs/heads/master@{#14276}

TBR=ossu@webrtc.org,henrik.lundin@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:5801

Review-Url: https://codereview.webrtc.org/2346173002
Cr-Commit-Position: refs/heads/master@{#14277}
diff --git a/webrtc/modules/audio_coding/acm2/acm_receiver.cc b/webrtc/modules/audio_coding/acm2/acm_receiver.cc
index 042e8c9..b89091f 100644
--- a/webrtc/modules/audio_coding/acm2/acm_receiver.cc
+++ b/webrtc/modules/audio_coding/acm2/acm_receiver.cc
@@ -314,15 +314,19 @@
 int AcmReceiver::DecoderByPayloadType(uint8_t payload_type,
                                       CodecInst* codec) const {
   rtc::CritScope lock(&crit_sect_);
-  const rtc::Optional<CodecInst> ci = neteq_->GetDecoder(payload_type);
-  if (ci) {
-    *codec = *ci;
-    return 0;
-  } else {
+  auto it = decoders_.find(payload_type);
+  if (it == decoders_.end()) {
     LOG(LERROR) << "AcmReceiver::DecoderByPayloadType "
                 << static_cast<int>(payload_type);
     return -1;
   }
+  const Decoder& decoder = it->second;
+  *codec = *RentACodec::CodecInstById(
+      *RentACodec::CodecIdFromIndex(decoder.acm_codec_id));
+  codec->pltype = decoder.payload_type;
+  codec->channels = decoder.channels;
+  codec->plfreq = decoder.sample_rate_hz;
+  return 0;
 }
 
 int AcmReceiver::EnableNack(size_t max_nack_list_size) {
diff --git a/webrtc/modules/audio_coding/acm2/acm_receiver_unittest_oldapi.cc b/webrtc/modules/audio_coding/acm2/acm_receiver_unittest_oldapi.cc
index aa46607..5622fc1 100644
--- a/webrtc/modules/audio_coding/acm2/acm_receiver_unittest_oldapi.cc
+++ b/webrtc/modules/audio_coding/acm2/acm_receiver_unittest_oldapi.cc
@@ -174,11 +174,10 @@
 TEST_F(AcmReceiverTestOldApi, MAYBE_AddCodecGetCodec) {
   // Add codec.
   for (size_t n = 0; n < codecs_.size(); ++n) {
-    if (n & 0x1) {  // Just add codecs with odd index.
-      EXPECT_EQ(
-          0, receiver_->AddCodec(n, codecs_[n].pltype, codecs_[n].channels,
-                                 codecs_[n].plfreq, NULL, codecs_[n].plname));
-    }
+    if (n & 0x1)  // Just add codecs with odd index.
+      EXPECT_EQ(0,
+                receiver_->AddCodec(n, codecs_[n].pltype, codecs_[n].channels,
+                                    codecs_[n].plfreq, NULL, ""));
   }
   // Get codec and compare.
   for (size_t n = 0; n < codecs_.size(); ++n) {
@@ -210,9 +209,9 @@
   // Register the same codec with different payloads.
   EXPECT_EQ(0, receiver_->AddCodec(codec1.id, codec1.inst.pltype,
                                    codec1.inst.channels, codec1.inst.plfreq,
-                                   nullptr, codec1.inst.plname));
+                                   nullptr, ""));
   EXPECT_EQ(0, receiver_->AddCodec(codec1.id, codec2.pltype, codec2.channels,
-                                   codec2.plfreq, NULL, codec2.plname));
+                                   codec2.plfreq, NULL, ""));
 
   // Both payload types should exist.
   EXPECT_EQ(0,
@@ -236,10 +235,10 @@
   // Register the same payload type with different codec ID.
   EXPECT_EQ(0, receiver_->AddCodec(codec1.id, codec1.inst.pltype,
                                    codec1.inst.channels, codec1.inst.plfreq,
-                                   nullptr, codec1.inst.plname));
+                                   nullptr, ""));
   EXPECT_EQ(0, receiver_->AddCodec(codec2.id, codec2.inst.pltype,
                                    codec2.inst.channels, codec2.inst.plfreq,
-                                   nullptr, codec2.inst.plname));
+                                   nullptr, ""));
 
   // Make sure that the last codec is used.
   EXPECT_EQ(0,
@@ -257,7 +256,7 @@
   const int payload_type = codec.inst.pltype;
   EXPECT_EQ(
       0, receiver_->AddCodec(codec.id, codec.inst.pltype, codec.inst.channels,
-                             codec.inst.plfreq, nullptr, codec.inst.plname));
+                             codec.inst.plfreq, nullptr, ""));
 
   // Remove non-existing codec should not fail. ACM1 legacy.
   EXPECT_EQ(0, receiver_->RemoveCodec(payload_type + 1));