[Chromecast] Always require decryption for mixer backend

Bug: internal b/77551062
Test: manual
Change-Id: I95d6caa7c2d33c682d118cfa3c4096ac307886aa
Reviewed-on: https://chromium-review.googlesource.com/998836Reviewed-by: Sergey Volk <servolk@chromium.org>
Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
Commit-Queue: James West <jameswest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548582}

chromecast/media/cma/backend/audio_decoder_for_mixer.cc

@@ -57,6 +57,11 @@ const int64_t kNoPendingOutput = -1;
 
 }  // namespace
 
+// static
+bool MediaPipelineBackend::AudioDecoder::RequiresDecryption() {
+  return true;
+}
+
 AudioDecoderForMixer::RateShifterInfo::RateShifterInfo(float playback_rate)
     : rate(playback_rate), input_frames(0), output_frames(0) {}
 

chromecast/media/cma/backend/audio_decoder_wrapper.cc

@@ -107,7 +107,9 @@ void AudioDecoderWrapper::GetStatistics(Statistics* statistics) {
 }
 
 bool AudioDecoderWrapper::RequiresDecryption() {
-  return decoder_.IsUsingSoftwareDecoder();
+  return (MediaPipelineBackend::AudioDecoder::RequiresDecryption &&
+          MediaPipelineBackend::AudioDecoder::RequiresDecryption()) ||
+         decoder_.IsUsingSoftwareDecoder();
 }
 
 }  // namespace media

chromecast/public/media/media_pipeline_backend.h

@@ -154,6 +154,11 @@ class MediaPipelineBackend {
     static int64_t GetMinimumBufferedTime(const AudioConfig& config)
         __attribute__((__weak__));
 
+    // Returns true if the audio decoder requires that encrypted buffers be
+    // decrypted before being passed to PushBuffer().
+    CHROMECAST_EXPORT static bool RequiresDecryption()
+        __attribute__((__weak__));
+
    protected:
     ~AudioDecoder() override {}
   };