Switch from GTEST_FLAG to GTEST_FLAG_SET.

::testing::GTEST_FLAG is deprecated and it will be removed in future
versions of gtest.

Bug: None
Change-Id: Icb2ad2a7607073cf9ad63753a4de34f37bda411c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/227083
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34600}
diff --git a/rtc_base/thread_unittest.cc b/rtc_base/thread_unittest.cc
index 86c14c8..ce79cf7 100644
--- a/rtc_base/thread_unittest.cc
+++ b/rtc_base/thread_unittest.cc
@@ -446,7 +446,7 @@
 // not deadlock but crash.
 #if RTC_DCHECK_IS_ON && GTEST_HAS_DEATH_TEST && !defined(WEBRTC_ANDROID)
 TEST(ThreadTest, TwoThreadsInvokeDeathTest) {
-  ::testing::GTEST_FLAG(death_test_style) = "threadsafe";
+  GTEST_FLAG_SET(death_test_style, "threadsafe");
   AutoThread thread;
   Thread* main_thread = Thread::Current();
   auto other_thread = Thread::CreateWithSocketServer();
@@ -457,7 +457,7 @@
 }
 
 TEST(ThreadTest, ThreeThreadsInvokeDeathTest) {
-  ::testing::GTEST_FLAG(death_test_style) = "threadsafe";
+  GTEST_FLAG_SET(death_test_style, "threadsafe");
   AutoThread thread;
   Thread* first = Thread::Current();