Ensure that SequencedWorkerPools in tests don't outlive their tests

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 # running overnight and removing outdated bugs/suppressions.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 377 matching lines @@
 
 # Histogram macros involve string comparison in debug mode.
 {
    bug_115987b [benign races in Histogram in SequencedWorkerPool]
    ThreadSanitizer:Race
    ...
    fun:std::operator==
    fun:base::SequencedWorkerPool::*
 }
 
-{
-   bug_115987c
-   ThreadSanitizer:Race
-   fun:logging::GetMinLogLevel
-   fun:base::ConditionVariable::*
-   fun:base::SequencedWorkerPool::Inner::ThreadLoop
-   fun:base::SequencedWorkerPool::Worker::Run
-   fun:base::SimpleThread::ThreadMain
-   fun:base::::ThreadFunc
-}
-
-
 # 3. Suppressions for real chromium bugs that are not yet fixed.
 ############################
 # Real races in Chromium
 {
   bug_23433
   ThreadSanitizer:Race
   fun:*logging*SetMinLogLevel*
 }
 
 {
@@ skipping 447 matching lines @@
   bug_116421
   ThreadSanitizer:Race
   fun:talk_base::Event::EnsureInitialized
 }
 {
   bug_116559
   ThreadSanitizer:Race
   fun:logging::::LoggingTest_Dcheck_Test::TestBody
   fun:testing::internal::HandleSehExceptionsInMethodIfSupported
 }