[ABANDONED] Call Microtask::performCheckpoint for each worker task.

Source/core/dom/Microtask.cpp

Index: Source/core/dom/Microtask.cpp
diff --git a/Source/core/dom/Microtask.cpp b/Source/core/dom/Microtask.cpp
index bbfb00df0df387155ff21d0dc56ec1f724c3547b..642907ef212aa14a11056792afc1c8714ebef508 100644
--- a/Source/core/dom/Microtask.cpp
+++ b/Source/core/dom/Microtask.cpp
@@ -48,6 +48,10 @@ void Microtask::performCheckpoint()
 
     v8::HandleScope handleScope(isolate);
     v8::Local<v8::Context> context = isolateData->ensureDomInJSContext();
+    if (context.IsEmpty()) {
+        // The script execution has been terminated.
+        return;
+    }
     v8::Context::Scope scope(context);
     v8::V8::RunMicrotasks(isolate);