Add a couple of suppressions to make the MFYI waterfall greener

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 # running overnight and removing outdated bugs/suppressions.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 1013 matching lines @@
   fun:crypto::RSAPrivateKey::CreateWithParams
   fun:crypto::RSAPrivateKey::Create
   fun:crypto::RSAPrivateKey::Create
   fun:remoting::RsaKeyPair::Generate
   fun:remoting::Me2MeNativeMessagingHost::ProcessGenerateKeyPair
   fun:remoting::Me2MeNativeMessagingHost::ProcessMessage
   fun:remoting::Me2MeNativeMessagingHost::ProcessMessage
   fun:base::internal::RunnableAdapter::Run
 }
 {
-  bug_344704
+  bug_344704_a
   ThreadSanitizer:Race
   fun:base::Thread::message_loop
   fun:printing::PrintJob::UpdatePrintedDocument
   fun:printing::PrintJob::ControlledWorkerShutdown
   fun:printing::PrintJob::Stop
   fun:PrintJobTest_SimplePrint_Test::TestBody
 }
 {
+  bug_344704_b
+  ThreadSanitizer:Race
+  fun:scoped_refptr::operator=
+  fun:base::MessageLoop::~MessageLoop
+  fun:base::MessageLoop::~MessageLoop
+  fun:base::DefaultDeleter::operator()
+  fun:base::internal::scoped_ptr_impl::~scoped_ptr_impl
+  fun:scoped_ptr::~scoped_ptr
+  fun:base::Thread::ThreadMain
+}
+{
   bug_350982
   ThreadSanitizer:Race
   fun:change_state
   fun:vp9_worker_sync
   fun:decode_tile
   fun:decode_tiles
   fun:vp9_decode_frame
 }
 {
   bug_343802
   ThreadSanitizer:Race
   ...
   fun:base::debug::TraceLog::GetCategoryGroupEnabledInternal
 }