Add codec name to CodecSpecificInfo and get the codec name stats from there instead.

BUG=webrtc:5687

Review-Url: https://codereview.webrtc.org/2253563002
Cr-Commit-Position: refs/heads/master@{#14012}

webrtc/test/fake_encoder.cc

diff --git a/webrtc/test/fake_encoder.cc b/webrtc/test/fake_encoder.cc
index a3fb768..0a3f34e 100644
--- a/webrtc/test/fake_encoder.cc
+++ b/webrtc/test/fake_encoder.cc
@@ -108,6 +108,7 @@
     if (min_stream_bits > bits_available && i > 0)
       continue;
     assert(callback_ != NULL);
+    specifics.codec_name = ImplementationName();
     if (callback_->Encoded(encoded, &specifics, NULL) != 0)
       return -1;
     bits_available -= std::min(encoded._length * 8, bits_available);