Revert "Disable some flaky thread pool/group tests on Windows."

This reverts commit 15af2fe9.

Reason for revert: Tests should no longer be flaky after https://chromium.googlesource.com/chromium/src.git/+/9cc2312030ea55160dd559fff630689b7165a472

Original change's description:
> Disable some flaky thread pool/group tests on Windows.
> 
> 
> BUG:1064953
> TBR=etiennep@chromium.org
> 
> Change-Id: Ibcb1f4c184045cc429d733e78f05ff892ca1a018
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2121380
> Reviewed-by: Tim Schumann <tschumann@chromium.org>
> Commit-Queue: Tim Schumann <tschumann@chromium.org>
> Auto-Submit: Tim Schumann <tschumann@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#753630}

TBR=tschumann@chromium.org,etiennep@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I6b6a2aa37eb373bf5a981b9b5ba3fab362a09637
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2127490Reviewed-by: Etienne Pierre-Doray <etiennep@chromium.org>
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#754510}

base/task/thread_pool/job_task_source_unittest.cc

@@ -386,13 +386,7 @@ TEST_F(ThreadPoolJobTaskSourceTest, MaxConcurrencyStagnateIfShouldYield) {
 
 // Verifies that a missing call to NotifyConcurrencyIncrease() causes a DCHECK
 // death after a timeout.
-// TODO(crbug.com/1064953): Flaky on Windows.
-#if defined(OS_WIN)
-#define MAYBE_InvalidConcurrency DISABLED_InvalidConcurrency
-#else
-#define MAYBE_InvalidConcurrency InvalidConcurrency
-#endif
-TEST_F(ThreadPoolJobTaskSourceTest, MAYBE_InvalidConcurrency) {
+TEST_F(ThreadPoolJobTaskSourceTest, InvalidConcurrency) {
   testing::FLAGS_gtest_death_test_style = "threadsafe";
 
   scoped_refptr<test::MockJobTask> job_task;
@@ -422,14 +416,7 @@ TEST_F(ThreadPoolJobTaskSourceTest, MAYBE_InvalidConcurrency) {
 
 // Verifies that a stale concurrency with no call to NotifyConcurrencyIncrease()
 // causes a DCHECK death after a timeout.
-  
-// TODO(crbug.com/1064953): Flaky on Windows.
-#if defined(OS_WIN)
-#define MAYBE_StaleConcurrency DISABLED_StaleConcurrency
-#else
-#define MAYBE_StaleConcurrency StaleConcurrency
-#endif
-TEST_F(ThreadPoolJobTaskSourceTest, MAYBE_StaleConcurrency) {
+TEST_F(ThreadPoolJobTaskSourceTest, StaleConcurrency) {
   testing::FLAGS_gtest_death_test_style = "threadsafe";
 
   auto task_source = MakeRefCounted<JobTaskSource>(

base/task/thread_pool/thread_group_unittest.cc

@@ -806,13 +806,7 @@ TEST_P(ThreadGroupTest, JoinJobTaskSource) {
 
 // Verify that finishing work outside of a job unblocks workers with a stale
 // max concurrency.
-// TODO(crbug.com/1064953): Flaky on Windows.
-#if defined(OS_WIN)
-#define MAYBE_JoinJobTaskSourceStaleConcurrency DISABLED_JoinJobTaskSourceStaleConcurrency
-#else
-#define MAYBE_JoinJobTaskSourceStaleConcurrency JoinJobTaskSourceStaleConcurrency
-#endif
-TEST_P(ThreadGroupTest, MAYBE_JoinJobTaskSourceStaleConcurrency) {
+TEST_P(ThreadGroupTest, JoinJobTaskSourceStaleConcurrency) {
   StartThreadGroup();
 
   WaitableEvent thread_running;