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

Source/core/dom/Microtask.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 30 matching lines @@
 {
     v8::Isolate* isolate = v8::Isolate::GetCurrent();
     V8PerIsolateData* isolateData = V8PerIsolateData::from(isolate);
     ASSERT(isolateData);
     if (isolateData->recursionLevel() || isolateData->performingMicrotaskCheckpoint())
         return;
     isolateData->setPerformingMicrotaskCheckpoint(true);
 
     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);
 
     isolateData->setPerformingMicrotaskCheckpoint(false);
 }
 
 COMPILE_ASSERT(sizeof(void*) == sizeof(MicrotaskCallback), VoidPtrAndFunctionPtrAreSameSize);
 
 static void microtaskFunctionCallback(const v8::FunctionCallbackInfo<v8::Value>& info)
 {
@@ skipping 10 matching lines @@
     v8::HandleScope handleScope(isolate);
     v8::Local<v8::Context> context = isolateData->ensureDomInJSContext();
     v8::Context::Scope scope(context);
     v8::Local<v8::External> handler =
         v8::External::New(isolate,
             reinterpret_cast<void*>(reinterpret_cast<intptr_t>(callback)));
     v8::V8::EnqueueMicrotask(isolate, v8::Function::New(isolate, &microtaskFunctionCallback, handler));
 }
 
 } // namespace WebCore