[test] Remove FlagScope use in test-api.cc

Resetting the flag in the scope desctructor causes concurrent access to
the flag value, triggering a TSAN failure when
--stress-concurrent-inlining is on. The behaviour of the stress flag
was changed in crrev.com/c/2824440 to improve test coverage, so this
CL replaces the scope usage with simple flag assignment.

Bug: v8:11740
Change-Id: Ie706edaa50486dd3b6eaabc9d1f26a8d03068418
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2882801Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74461}

test/cctest/test-api.cc

@@ -28192,12 +28192,12 @@ TEST(FastApiStackSlot) {
 #ifndef V8_LITE_MODE
   if (i::FLAG_jitless) return;
 
-  FLAG_SCOPE_EXTERNAL(opt);
-  FLAG_SCOPE_EXTERNAL(turbo_fast_api_calls);
-  FLAG_SCOPE_EXTERNAL(allow_natives_syntax);
+  v8::internal::FLAG_opt = true;
+  v8::internal::FLAG_turbo_fast_api_calls = true;
+  v8::internal::FLAG_allow_natives_syntax = true;
   // Disable --always_opt, otherwise we haven't generated the necessary
   // feedback to go down the "best optimization" path for the fast call.
-  UNFLAG_SCOPE_EXTERNAL(always_opt);
+  v8::internal::FLAG_always_opt = false;
 
   v8::Isolate* isolate = CcTest::isolate();
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
@@ -28243,12 +28243,12 @@ TEST(FastApiCalls) {
 #ifndef V8_LITE_MODE
   if (i::FLAG_jitless) return;
 
-  FLAG_SCOPE_EXTERNAL(opt);
-  FLAG_SCOPE_EXTERNAL(turbo_fast_api_calls);
-  FLAG_SCOPE_EXTERNAL(allow_natives_syntax);
+  v8::internal::FLAG_opt = true;
+  v8::internal::FLAG_turbo_fast_api_calls = true;
+  v8::internal::FLAG_allow_natives_syntax = true;
   // Disable --always_opt, otherwise we haven't generated the necessary
   // feedback to go down the "best optimization" path for the fast call.
-  UNFLAG_SCOPE_EXTERNAL(always_opt);
+  v8::internal::FLAG_always_opt = false;
 
   v8::Isolate* isolate = CcTest::isolate();
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);