Update tsan suppressions due to r273571.

tools/valgrind/tsan/suppressions.txt

 # There are a few kinds of suppressions in this file.
 # 1. third party stuff we have no control over
 #
 # 2. intentional unit test errors, or stuff that is somehow a false positive
 # in our own code, or stuff that is so trivial it's not worth fixing
 #
 # 3. Suppressions for real chromium bugs that are not yet fixed.
 # These should all be in chromium's bug tracking system (but a few aren't yet).
 # Periodically we should sweep this file and the bug tracker clean by
 # running overnight and removing outdated bugs/suppressions.
@@ skipping 810 matching lines @@
   fun:base::internal::RunnableAdapter::Run
 }
 {
   bug_137701
   ThreadSanitizer:Race
   ...
   fun:_output_*
   fun:_vsnprintf_helper
 }
 {
-  bug_137973_a
-  ThreadSanitizer:Race
-  fun:media::Pipeline::OnVideoTimeUpdate
-  fun:base::internal::RunnableAdapter::Run
-}
-{
-  bug_137973_b
-  ThreadSanitizer:Race
-  fun:media::Pipeline::SetState
-  fun:media::Pipeline::StopTask
-  fun:base::internal::RunnableAdapter::Run
-}
-{
-  bug_137973_c
-  ThreadSanitizer:Race
-  fun:media::Pipeline::SetState
-  fun:media::Pipeline::SeekTask
-  fun:base::internal::RunnableAdapter::Run
-}
-{
   bug_144894
   ThreadSanitizer:Race
   fun:av_parser_close
   fun:avcodec_open2
   fun:avformat_find_stream_info
   fun:media::FFmpegConfigHelper::SetupStreamConfigs
   fun:media::FFmpegConfigHelper::Parse
   fun:media::WebMStreamParser::ParseInfoAndTracks
   fun:media::WebMStreamParser::Parse
   fun:media::ChunkDemuxer::AppendData
@@ skipping 206 matching lines @@
   fun:decode_tile
   fun:decode_tiles
   fun:vp9_decode_frame
 }
 {
   bug_343802
   ThreadSanitizer:Race
   ...
   fun:base::debug::TraceLog::GetCategoryGroupEnabledInternal
 }