Change LS_ERROR to LS_WARNING for unsupported decoder formats

There is currently an error reported about unsupported formats
for most users when an WebRTC connection is setup. This CL
changes the error to a warning.

The reason is that some H264 profiles are supported in hardware
but not in software. When the decoder is created we will try to
create pair of both software and hardware decoders for the
union of supported formats. The creation of the software
decoder will then fail. There is a small risk that this leads
to errors later but only in rare circumstances. Most of the time
this log line only confuses consumers as well as developers.

Bug: none
Change-Id: Ib2119016fa91bc270437a2bcf7892e9fdd7c419c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/196645
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Commit-Queue: Johannes Kron <kron@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32800}
diff --git a/media/engine/internal_decoder_factory.cc b/media/engine/internal_decoder_factory.cc
index d512b73..1c08484 100644
--- a/media/engine/internal_decoder_factory.cc
+++ b/media/engine/internal_decoder_factory.cc
@@ -56,7 +56,8 @@
 std::unique_ptr<VideoDecoder> InternalDecoderFactory::CreateVideoDecoder(
     const SdpVideoFormat& format) {
   if (!IsFormatSupported(GetSupportedFormats(), format)) {
-    RTC_LOG(LS_ERROR) << "Trying to create decoder for unsupported format";
+    RTC_LOG(LS_WARNING) << "Trying to create decoder for unsupported format. "
+                        << format.ToString();
     return nullptr;
   }