Replace media::Limits struct with media::limits namespace and update documentation.

media/filters/ffmpeg_demuxer.cc

Index: media/filters/ffmpeg_demuxer.cc
diff --git a/media/filters/ffmpeg_demuxer.cc b/media/filters/ffmpeg_demuxer.cc
index e33bada6f1b74043169fdedf0510b91856949267..08476ba43ed457fbb1cef214ad24206bbe6dbe58 100644
--- a/media/filters/ffmpeg_demuxer.cc
+++ b/media/filters/ffmpeg_demuxer.cc
@@ -522,7 +522,7 @@ void FFmpegDemuxer::InitializeTask(DataSource* data_source,
     // The duration is not a valid value. Assume that this is a live stream
     // and set duration to the maximum int64 number to represent infinity.

[Ami GONE FROM CHROMIUM, 2011/12/03 02:11:38]

This is crazy.  If we want \infty we should define a kInfinity, and probably use
an obviously-bogus value like -1.

[scherkus (not reviewing), 2011/12/06 02:05:57]

That makes sense for durations, but if we're going to pick sentinel values why
not use a value that's as close to infinity as we're going to get? it has the
nice property of being able to use std::max()/min()

     max_duration = base::TimeDelta::FromMicroseconds(
-        Limits::kMaxTimeInMicroseconds);
+        limits::kMaxTimeInMicroseconds);
   }
 
   // Some demuxers, like WAV, do not put timestamps on their frames. We
@@ -562,7 +562,7 @@ int FFmpegDemuxer::GetBitrate() {
   // If there isn't a bitrate set in the container or streams, but there is a
   // valid duration, approximate the bitrate using the duration.
   if (max_duration_.InMilliseconds() > 0 &&
-      max_duration_.InMicroseconds() < Limits::kMaxTimeInMicroseconds) {
+      max_duration_.InMicroseconds() < limits::kMaxTimeInMicroseconds) {

[Ami GONE FROM CHROMIUM, 2011/12/03 02:11:38]

This would be a lot clearer as != kInfinity IMO.

[scherkus (not reviewing), 2011/12/06 02:05:57]

Done.

     int64 filesize_in_bytes;
     if (GetSize(&filesize_in_bytes))
       return 8000 * filesize_in_bytes / max_duration_.InMilliseconds();

[Ami GONE FROM CHROMIUM, 2011/12/03 02:11:38]

This can SIGFPE b/c the >0 check is done in microseconds but here we divide by
milliseconds.

[scherkus (not reviewing), 2011/12/06 02:05:57]

Done.