Replace Pipeline::SetNetworkActivity() with BufferedDataSource -> WebMediaPlayerImpl callback.

media/filters/chunk_demuxer_unittest.cc

Index: media/filters/chunk_demuxer_unittest.cc
diff --git a/media/filters/chunk_demuxer_unittest.cc b/media/filters/chunk_demuxer_unittest.cc
index 6eed52c43c58107e4b293c5ccbce2595a1e785f5..18faa75adfeab6a819573c8b3d28bb34720c60d0 100644
--- a/media/filters/chunk_demuxer_unittest.cc
+++ b/media/filters/chunk_demuxer_unittest.cc
@@ -185,8 +185,6 @@ class ChunkDemuxerTest : public testing::Test {
     CHECK(length);
     EXPECT_CALL(host_, AddBufferedByteRange(_, _)).Times(AnyNumber())
         .WillRepeatedly(SaveArg<1>(&buffered_bytes_));
-    EXPECT_CALL(host_, SetNetworkActivity(true))
-        .Times(AnyNumber());
     return demuxer_->AppendData(kSourceId, data, length);
   }