media: Remove confusing MediaLog message in DecryptingDemuxerStream

Today on systems where we use AesDecryptor for Clear Key key system and
MojoCdm for other key systems, the DecoderSelector will always try to
see whether there is a Decryptor exposed by the CDM to decrypt the
stream directly (e.g. AesDecryptor). If not, it'll fallback to MojoCdm
which will typically will decrypt and decode in the remote process.

Hence, "no decryptor" exposed by a CDM is normal. Previously we report
this as a "debug" message in MediaLog, but it often causes confusions.

This CL changes this MediaLog log to DVLOG to avoid such confusion.

Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: If434dd7ae5bc7e76ab68c964190b465bf55d9185
Reviewed-on: https://chromium-review.googlesource.com/803671Reviewed-by: John Rummell <jrummell@chromium.org>
Reviewed-by: Frank Liberato <liberato@chromium.org>
Commit-Queue: Xiaohan Wang <xhwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521146}

media/filters/decrypting_demuxer_stream.cc

@@ -58,7 +58,7 @@ void DecryptingDemuxerStream::Initialize(DemuxerStream* stream,
   InitializeDecoderConfig();
 
   if (!cdm_context->GetDecryptor()) {
-    MEDIA_LOG(DEBUG, media_log_) << GetDisplayName() << ": no decryptor";
+    DVLOG(2) << __func__ << ": no decryptor";
     state_ = kUninitialized;
     base::ResetAndReturn(&init_cb_).Run(DECODER_ERROR_NOT_SUPPORTED);
     return;

media/filters/decrypting_demuxer_stream_unittest.cc

@@ -313,7 +313,6 @@ TEST_F(DecryptingDemuxerStreamTest, Initialize_CdmWithoutDecryptor) {
   AudioDecoderConfig input_config(kCodecVorbis, kSampleFormatPlanarF32,
                                   CHANNEL_LAYOUT_STEREO, 44100,
                                   EmptyExtraData(), AesCtrEncryptionScheme());
-  EXPECT_MEDIA_LOG(HasSubstr("DecryptingDemuxerStream: no decryptor"));
   InitializeAudioAndExpectStatus(input_config, DECODER_ERROR_NOT_SUPPORTED);
 }