media config: expand is_encrypted to a struct.

media/base/audio_decoder_config.h

Index: media/base/audio_decoder_config.h
diff --git a/media/base/audio_decoder_config.h b/media/base/audio_decoder_config.h
index 71c893028fff82148b72eb706daad1f69e68d346..f93d0008b0d16a4ba759d5903cdad6c4ba87edb4 100644
--- a/media/base/audio_decoder_config.h
+++ b/media/base/audio_decoder_config.h
@@ -14,6 +14,7 @@
 #include "base/time/time.h"
 #include "media/base/audio_codecs.h"
 #include "media/base/channel_layout.h"
+#include "media/base/encryption_scheme.h"
 #include "media/base/media_export.h"
 #include "media/base/sample_format.h"
 
@@ -34,7 +35,7 @@ class MEDIA_EXPORT AudioDecoderConfig {
                      ChannelLayout channel_layout,
                      int samples_per_second,
                      const std::vector<uint8_t>& extra_data,
-                     bool is_encrypted);
+                     const EncryptionScheme& encryption_scheme);
 
   AudioDecoderConfig(const AudioDecoderConfig& other);
 
@@ -46,7 +47,7 @@ class MEDIA_EXPORT AudioDecoderConfig {
                   ChannelLayout channel_layout,
                   int samples_per_second,
                   const std::vector<uint8_t>& extra_data,
-                  bool is_encrypted,
+                  const EncryptionScheme& encryption_scheme,
                   base::TimeDelta seek_preroll,
                   int codec_delay);
 
@@ -79,7 +80,12 @@ class MEDIA_EXPORT AudioDecoderConfig {
   // Whether the audio stream is potentially encrypted.
   // Note that in a potentially encrypted audio stream, individual buffers
   // can be encrypted or not encrypted.
-  bool is_encrypted() const { return is_encrypted_; }
+  bool is_encrypted() const;

[ddorwin, 2016/03/02 23:24:05]

From PS13: I guess we should look for places where we expect it to be true in
tests and then check the other members in those cases.

[dougsteed, 2016/03/03 04:45:00]

OK, I'll scan through all instances with that in mind ....
... looked through all occurrences of is_encrypted() applied to
{Audio|Video}DecoderConfig.

Most of them are essentially asserting that it is not encrypted. I changed
media/filters/source_buffer_stream.cc to check the whole encryption_scheme
rather than just is_encrypted.
A few of the call sites are using is_encrypted() to evaluate a higher-level
notion of "IsEncrypted". I didn't follow all those paths.
The ones that I would like your input on are in: PpapiDecryptor,
DecryptingVideoDecoder, VideoDecodeAccelerator.

[ddorwin, 2016/03/03 18:38:04]

Thanks.

Those should three be fine since we only support CTR no pattern there. I was
specifically referring to tests. If there were any tests that expected true,
then we should check the mode and pattern (almost certainly CTR and none,
respectively).

[dougsteed, 2016/03/04 19:07:29]

In many cases the test uses a boolean to decide whether it should be configured
to use encryption, and then uses an EXPECT with the boolean is_encrypted to
verify whether that was done correctly. It doesn't seem to be testing much
outside the test itself. I didn't see any where I thought it would be useful to
verify the mode. 

Please take a quick peek yourself and see if you agree.

+
+  // Encryption scheme used for encrypted buffers.
+  const EncryptionScheme& encryption_scheme() const {
+    return encryption_scheme_;
+  }
 
  private:
   AudioCodec codec_;
@@ -89,7 +95,7 @@ class MEDIA_EXPORT AudioDecoderConfig {
   int samples_per_second_;
   int bytes_per_frame_;
   std::vector<uint8_t> extra_data_;
-  bool is_encrypted_;
+  EncryptionScheme encryption_scheme_;
 
   // |seek_preroll_| is the duration of the data that the decoder must decode
   // before the decoded data is valid.