TSAN: Suppress error in ThreadWatcher::StartWatching.

tools/valgrind/tsan/suppressions.txt

 ############################
 # Real races in Chromium
 {
   bug_23433
   ThreadSanitizer:Race
   fun:*logging*SetMinLogLevel*
 }
 
 {
   bug_24419
@@ skipping 114 matching lines @@
   fun:sync_api::SyncManager::SyncInternal::*
 }
 
 {
   bug_82279
   ThreadSanitizer:Race
   fun:ObserverListBase::Iterator::Iterator
   fun:syncable::BaseTransaction::NotifyTransactionChangingAndEnding
 }
 
+{
+  bug_83564
+  ThreadSanitizer:Race
+  fun:base::Thread::message_loop
+  fun:BrowserThread::IsMessageLoopValid
+  fun:ThreadWatcherList::StartWatchingAll
+}
+
 ############################
 # Benign races in Chromium
 {
   bug_61179 [benign race on tracked_objects::Births]
   ThreadSanitizer:Race
   fun:tracked_objects::Births::*Birth*
 }
 
 {
   bug_62694 [benign races in Histogram in CookieMonster]
@@ skipping 361 matching lines @@
   tsanbug_62a
   ThreadSanitizer:Race
   fun:__memset_sse2
 }
 
 {
   tsanbug_62b
   ThreadSanitizer:Race
   fun:__GI_memcpy
 }