Allow setContentDecryptionModule() to get called when setting is done.

media/filters/decrypting_audio_decoder.cc

Index: media/filters/decrypting_audio_decoder.cc
diff --git a/media/filters/decrypting_audio_decoder.cc b/media/filters/decrypting_audio_decoder.cc
index 79d82093302c313de8265bdf27408a76d2f0429e..ee50e2edac8ff6d5502790a2644049acd4975ef3 100644
--- a/media/filters/decrypting_audio_decoder.cc
+++ b/media/filters/decrypting_audio_decoder.cc
@@ -166,7 +166,9 @@ DecryptingAudioDecoder::~DecryptingAudioDecoder() {
     base::ResetAndReturn(&reset_cb_).Run();
 }
 
-void DecryptingAudioDecoder::SetDecryptor(Decryptor* decryptor) {
+void DecryptingAudioDecoder::SetDecryptor(
+    Decryptor* decryptor,
+    const DecryptorAttachedCB& decryptor_attached_cb) {
   DVLOG(2) << "SetDecryptor()";
   DCHECK(task_runner_->BelongsToCurrentThread());
   DCHECK_EQ(state_, kDecryptorRequested) << state_;
@@ -178,12 +180,14 @@ void DecryptingAudioDecoder::SetDecryptor(Decryptor* decryptor) {
   if (!decryptor) {
     base::ResetAndReturn(&init_cb_).Run(DECODER_ERROR_NOT_SUPPORTED);
     state_ = kError;
+    decryptor_attached_cb.Run(false);
     return;
   }
 
   decryptor_ = decryptor;
 
   InitializeDecoder();
+  decryptor_attached_cb.Run(true);
 }
 
 void DecryptingAudioDecoder::InitializeDecoder() {