Chromecast media pipeline: handle CENC "full sample encryption" case.

chromecast/media/cma/ipc_streamer/decoder_buffer_base_marshaller.cc

Index: chromecast/media/cma/ipc_streamer/decoder_buffer_base_marshaller.cc
diff --git a/chromecast/media/cma/ipc_streamer/decoder_buffer_base_marshaller.cc b/chromecast/media/cma/ipc_streamer/decoder_buffer_base_marshaller.cc
index 14eb742495f1ed97dd648749e14ba1252257d641..dc1f8f5714e926e16f254295000ddfe72d73b0ee 100644
--- a/chromecast/media/cma/ipc_streamer/decoder_buffer_base_marshaller.cc
+++ b/chromecast/media/cma/ipc_streamer/decoder_buffer_base_marshaller.cc
@@ -141,8 +141,24 @@ void DecoderBufferBaseMarshaller::Write(
       (buffer->decrypt_config() != NULL &&
        buffer->decrypt_config()->iv().size() > 0);
   CHECK(msg->WritePod(has_decrypt_config));
-  if (has_decrypt_config)
-    DecryptConfigMarshaller::Write(*buffer->decrypt_config(), msg);
+
+  if (has_decrypt_config) {
+    // DecryptConfig may contain 0 subsamples if all content is encrypted.
+    // Map this case to a single fully-encrypted "subsample" for more consistent
+    // backend handling.
+    if (buffer->decrypt_config()->subsamples().empty()) {
+      std::vector< ::media::SubsampleEntry> encrypted_subsample_list(1);
+      encrypted_subsample_list[0].clear_bytes = 0;
+      encrypted_subsample_list[0].cypher_bytes = buffer->data_size();
+      ::media::DecryptConfig full_sample_config(
+          buffer->decrypt_config()->key_id(),
+          buffer->decrypt_config()->iv(),
+          encrypted_subsample_list);
+      DecryptConfigMarshaller::Write(full_sample_config, msg);
+    } else {
+      DecryptConfigMarshaller::Write(*buffer->decrypt_config(), msg);
+    }
+  }
 
   CHECK(msg->WritePod(buffer->data_size()));
   CHECK(msg->WriteBuffer(buffer->data(), buffer->data_size()));