Reland "Replace reduce-memory mode in idle notification with delayed clean-up GC."

test/cctest/test-api.cc

Index: test/cctest/test-api.cc
diff --git a/test/cctest/test-api.cc b/test/cctest/test-api.cc
index 202c2193a46574ea0dbb530a2ab7d319f9eb1ea0..2bfdeabd42cd606a40e8242d120465dc0414a0ab 100644
--- a/test/cctest/test-api.cc
+++ b/test/cctest/test-api.cc
@@ -15361,6 +15361,7 @@ static void CreateGarbageInOldSpace() {
 
 // Test that idle notification can be handled and eventually collects garbage.
 TEST(TestIdleNotification) {
+  if (!i::FLAG_incremental_marking) return;
   const intptr_t MB = 1024 * 1024;
   const double IdlePauseInSeconds = 1.0;
   LocalContext env;
@@ -15371,6 +15372,9 @@ TEST(TestIdleNotification) {
   CHECK_GT(size_with_garbage, initial_size + MB);
   bool finished = false;
   for (int i = 0; i < 200 && !finished; i++) {
+    if (i < 10 && CcTest::heap()->incremental_marking()->IsStopped()) {
+      CcTest::heap()->StartIdleIncrementalMarking();
+    }
     finished = env->GetIsolate()->IdleNotificationDeadline(
         (v8::base::TimeTicks::HighResolutionNow().ToInternalValue() /
          static_cast<double>(v8::base::Time::kMicrosecondsPerSecond)) +