Worker: Stop using WorkerThread::TerminateAllWorkersForTesting() in unit tests

TerminateAllWorkersForTesting() causes deadlock depending on timing. This CL
replaces the function with a combination of TerminateForTesting() and
WaitForShutdownForTesting() that are equivalent to
TerminateAllWorkersForTesting() but don't acquire the lock.

TerminateAllWorkersForTesting() on the main thread calls WaitableEvent::Wait()
while that is holding the ThreadSetMutex(). The mutex is also referenced from
the worker thread during worker startup in InitializeOnWorkerThread(). Deadlock
happens when the main thread starts termination immediately before the worker
thread tries to acquire the lock to insert itself in the thread set.

Note: TerminateAllWorkersForTesting() is still used from LeakDetector. I'll try
to remove/change it in a separate CL.

Bug: 1003217
Change-Id: I7896057c1c65a830c621e120123558403a94c951
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1839224
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702767}

third_party/blink/renderer/core/workers/worker_thread_test.cc

@@ -276,7 +276,8 @@ TEST_F(WorkerThreadTest, SyncTerminate_OnIdle) {
   // idle.
   worker_thread_->WaitForInit();
 
-  WorkerThread::TerminateAllWorkersForTesting();
+  worker_thread_->TerminateForTesting();
+  worker_thread_->WaitForShutdownForTesting();
 
   // The worker thread may gracefully shut down before forcible termination
   // runs.
@@ -296,19 +297,19 @@ TEST_F(WorkerThreadTest, AsyncTerminate_ImmediatelyAfterStart) {
   EXPECT_EQ(ExitCode::kGracefullyTerminated, GetExitCode());
 }
 
-// Disabled due to flakiness: https://crbug.com/1003217.
-TEST_F(WorkerThreadTest, DISABLED_SyncTerminate_ImmediatelyAfterStart) {
+TEST_F(WorkerThreadTest, SyncTerminate_ImmediatelyAfterStart) {
   ExpectReportingCallsForWorkerPossiblyTerminatedBeforeInitialization();
   Start();
 
   // There are two possible cases depending on timing:
   // (1) If the thread hasn't been initialized on the worker thread yet,
-  // TerminateAllWorkersForTesting() should wait for initialization and shut
-  // down the thread immediately after that.
+  // TerminateForTesting() should wait for initialization and shut down the
+  // thread immediately after that.
   // (2) If the thread has already been initialized on the worker thread,
-  // TerminateAllWorkersForTesting() should synchronously forcibly terminates
-  // the worker execution.
-  WorkerThread::TerminateAllWorkersForTesting();
+  // TerminateForTesting() should synchronously forcibly terminates the worker
+  // script execution.
+  worker_thread_->TerminateForTesting();
+  worker_thread_->WaitForShutdownForTesting();
   ExitCode exit_code = GetExitCode();
   EXPECT_TRUE(ExitCode::kGracefullyTerminated == exit_code ||
               ExitCode::kSyncForciblyTerminated == exit_code);
@@ -343,9 +344,9 @@ TEST_F(WorkerThreadTest, SyncTerminate_WhileTaskIsRunning) {
   StartWithSourceCodeNotToFinish();
   reporting_proxy_->WaitUntilScriptEvaluation();
 
-  // TerminateAllWorkersForTesting() synchronously terminates the worker
-  // execution.
-  WorkerThread::TerminateAllWorkersForTesting();
+  // TerminateForTesting() synchronously terminates the worker script execution.
+  worker_thread_->TerminateForTesting();
+  worker_thread_->WaitForShutdownForTesting();
   EXPECT_EQ(ExitCode::kSyncForciblyTerminated, GetExitCode());
 }
 
@@ -362,9 +363,10 @@ TEST_F(WorkerThreadTest,
   EXPECT_TRUE(IsForcibleTerminationTaskScheduled());
   EXPECT_EQ(ExitCode::kNotTerminated, GetExitCode());
 
-  // TerminateAllWorkersForTesting() should overtake the scheduled forcible
-  // termination task.
-  WorkerThread::TerminateAllWorkersForTesting();
+  // TerminateForTesting() should overtake the scheduled forcible termination
+  // task.
+  worker_thread_->TerminateForTesting();
+  worker_thread_->WaitForShutdownForTesting();
   EXPECT_FALSE(IsForcibleTerminationTaskScheduled());
   EXPECT_EQ(ExitCode::kSyncForciblyTerminated, GetExitCode());
 }