[ThreadPool] Fix unlikely race in ThreadPoolImplTest.FileDescriptorWatcherNoOpsAfterShutdown

R=etiennep@chromium.org

Bug: 965717
Change-Id: Ie7185cd0afc819d612368c6ce168a1544b2a64af
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1654271
Commit-Queue: Gabriel Charette <gab@chromium.org>
Auto-Submit: Gabriel Charette <gab@chromium.org>
Reviewed-by: Etienne Pierre-Doray <etiennep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#668476}

base/task/thread_pool/thread_pool_impl_unittest.cc

@@ -767,6 +767,12 @@ TEST_P(ThreadPoolImplTest, FileDescriptorWatcherNoOpsAfterShutdown) {
   // Give a chance for the file watcher to fire before closing the handles.
   PlatformThread::Sleep(TestTimeouts::tiny_timeout());
 
+  // Need to join the ServiceThread before closing the pipes as the pipe
+  // becoming readable is observed on the ServiceThread and TSAN correctly
+  // identifies this as a race even though the above sleep makes it highly
+  // unlikely in practice.
+  TearDown();
+
   EXPECT_EQ(0, IGNORE_EINTR(close(pipes[0])));
   EXPECT_EQ(0, IGNORE_EINTR(close(pipes[1])));
 }

build/sanitizers/tsan_suppressions.cc

@@ -168,10 +168,6 @@ char kTSanDefaultSuppressions[] =
     // http://crbug.com/927330
     "race:net::(anonymous namespace)::g_network_change_notifier\n"
 
-    // https://crbug.com/965717
-    "race:base::internal::ThreadPoolImplTest_"
-    "FileDescriptorWatcherNoOpsAfterShutdown_Test::TestBody\n"
-
     // https://crbug.com/965722
     "race:content::(anonymous namespace)::CorruptDBRequestHandler\n"