[GC] Check for incremental marking when a GC is triggered on reaching the external allocation limit

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 9df749bbc98a7b5b39352161f2ea9dc7cd0cec28..bbd4aa19bce2ee3b00f6d2a03f41b6dc19c8a19d 100644
--- a/test/cctest/test-api.cc
+++ b/test/cctest/test-api.cc
@@ -12574,6 +12574,17 @@ THREADED_TEST(ExternalAllocatedMemory) {
 }
 
 
+TEST(Regress51719) {
+  i::FLAG_incremental_marking = false;
+  CcTest::InitializeVM();
+
+  const int64_t kTriggerGCSize =
+      v8::internal::Internals::kExternalAllocationLimit + 1;
+  v8::Isolate* isolate = CcTest::isolate();
+  isolate->AdjustAmountOfExternalAllocatedMemory(kTriggerGCSize);
+}
+
+
 // Regression test for issue 54, object templates with internal fields
 // but no accessors or interceptors did not get their internal field
 // count set on instances.