Remove mock_ffmpeg and update media unittests.

media/filters/ffmpeg_glue.cc

Index: media/filters/ffmpeg_glue.cc
diff --git a/media/filters/ffmpeg_glue.cc b/media/filters/ffmpeg_glue.cc
index 7f134e319e7e6973c8e75a2a490d7997223ca699..bd5590151fdf83319be9fb9cfbc7a0f5799cf7f1 100644
--- a/media/filters/ffmpeg_glue.cc
+++ b/media/filters/ffmpeg_glue.cc
@@ -146,6 +146,11 @@ FFmpegGlue* FFmpegGlue::GetInstance() {
   return Singleton<FFmpegGlue>::get();
 }
 
+// static
+URLProtocol* FFmpegGlue::url_protocol() {
+  return &kFFmpegURLProtocol;
+}
+
 std::string FFmpegGlue::AddProtocol(FFmpegURLProtocol* protocol) {
   base::AutoLock auto_lock(lock_);
   std::string key = GetProtocolKey(protocol);