Widen suppressions for another FFmpeg roll.

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 # running overnight and removing outdated bugs/suppressions.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 899 matching lines @@
   fun:base::debug::TraceSamplingThread::ThreadMain
 }
 {
   bug_225123
   ThreadSanitizer:Race
   fun:setlocale
   ...
   fun:gfx::GtkInitFromCommandLine
 }
 {
-  bug_239350
+  bug_239350_a
   ThreadSanitizer:Race
   fun:av_buffer_unref
   fun:av_frame_unref
   ...
 }
 {
+  bug_239350_b
+  ThreadSanitizer:Race
+  fun:av_buffer_get_opaque
+  fun:av_buffer_get_opaque
+  ...
+}
+{
   bug_256792
   ThreadSanitizer:Race
   fun:media::AudioManagerAlsa::~AudioManagerAlsa
   fun:content::MockAudioManager::~MockAudioManager
   fun:content::MockAudioManager::~MockAudioManager
   fun:base::DefaultDeleter*
   fun:base::internal::scoped_ptr_impl::~scoped_ptr_impl
   fun:scoped_ptr::~scoped_ptr
   fun:content::MediaStreamManagerTest::~MediaStreamManagerTest
   fun:content::MediaStreamManagerTest_MakeAndCancelMediaAccessRequest_Test::~MediaStreamManagerTest_MakeAndCancelMediaAccessRequest_Test
@@ skipping 123 matching lines @@
   fun:decode_tile
   fun:decode_tiles
   fun:vp9_decode_frame
 }
 {
   bug_343802
   ThreadSanitizer:Race
   ...
   fun:base::debug::TraceLog::GetCategoryGroupEnabledInternal
 }