Allow setting memory limits on media::DemuxerStream

media/base/fake_text_track_stream.cc

Index: media/base/fake_text_track_stream.cc
diff --git a/media/base/fake_text_track_stream.cc b/media/base/fake_text_track_stream.cc
index 214eec435bbcf8a5c20d91a86c50f374f19d992b..6bc9c95a684b39e17f91c1154f83038cb9844a31 100644
--- a/media/base/fake_text_track_stream.cc
+++ b/media/base/fake_text_track_stream.cc
@@ -44,6 +44,15 @@ VideoRotation FakeTextTrackStream::video_rotation() {
   return VIDEO_ROTATION_0;
 }
 
+int FakeTextTrackStream::GetMemoryLimit() const {
+  NOTIMPLEMENTED();

[chcunningham, 2015/06/11 18:56:55]

We're having to do this same override boilerplate in a few places. I'm newish to
the team, so this may be the preferred style, but I notice we have some
"default" implementations in demuxer_stream.cc. WDYT about making this a default
there and removing the duplicate overrides? (Matt, please comment on whether
this suggestion is stylistically correct).

[servolk, 2015/06/12 00:50:48]

Yeah, that's a good point. I was pondering this myself. I went with pure virtual
function initially to make it easier for me to catch all the places that might
need to be updated (and so I've added a proper implementation of
Get/SetMemoryLimit for DecryptingDemuxerStream and left a TODO in Mojo code),
but yeah, there are a lot of media::DemuxerStream implementations and some of
them (e.g. all the test/fake/mock implementation) don't care about this. So we
could probably go with a default definition in demuxer_stream.cc for now, we'll
just have to remember to implement this for any actual DemuxerStream
implementations as necessary.

[wolenetz, 2015/06/12 21:31:56]

I was pondering similarly.
Backing up a bit, ISTM the goal is that eventually all real DemuxerStreams
should have memory buffer limit control that is meaningful.
To discover any new DemuxerStream implementations that might crop-up over time,
ISTM that pure-virtual, non-default in DemuxerStream, with explicit need for
overrides (with TODOs for those that explicitly require implementation) in each
DemuxerStream implementation, while somewhat boilerplate, will ensure the build
won't work for some variant that might use a specialized DemuxerStream that
hasn't been discovered in this CL (prevents dynamic fragility). Test mocks will
need the boilerplate, but IMO, that's a necessary complexity that is warranted
by catching unexpected lack of implementations that might crop up.

+  return 0;
+}
+
+void FakeTextTrackStream::SetMemoryLimit(int memory_limit) {
+  NOTIMPLEMENTED();
+}
+
 void FakeTextTrackStream::SatisfyPendingRead(
     const base::TimeDelta& start,
     const base::TimeDelta& duration,