Add a basic version of Worklet#import.

third_party/WebKit/Source/modules/worklet/Worklet.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef Worklet_h
 #define Worklet_h
 
+#include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptWrappable.h"
+#include "core/dom/ActiveDOMObject.h"
+#include "core/frame/csp/ContentSecurityPolicy.h"
+#include "core/workers/WorkerScriptLoader.h"
 #include "modules/worklet/WorkletGlobalScope.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class ExecutionContext;
+class ScriptPromiseResolver;
+class WorkerScriptLoader;
 
-class Worklet final : public GarbageCollectedFinalized<Worklet>, public ScriptWrappable {
+class Worklet final : public GarbageCollectedFinalized<Worklet>, public ScriptWrappable, public ActiveDOMObject {
+    DEFINE_WRAPPERTYPEINFO();
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(Worklet);
     WTF_MAKE_NONCOPYABLE(Worklet);
-    DEFINE_WRAPPERTYPEINFO();
 public:
     // The ExecutionContext argument is the parent document of the Worklet. The
     // Worklet inherits the url and userAgent, from the document.
     static Worklet* create(ExecutionContext*);
 
+    ScriptPromise import(ScriptState*, const String& url);
+
+    // ActiveDOMObject
+    void stop() final;
+
     DECLARE_TRACE();
 
 private:
     explicit Worklet(ExecutionContext*);
 
+    void onResponse();
+    void onFinished(WorkerScriptLoader*, ScriptPromiseResolver*);
+
     RefPtrWillBeMember<WorkletGlobalScope> m_workletGlobalScope;
+    Vector<RefPtr<WorkerScriptLoader>> m_scriptLoaders;
+    HeapVector<Member<ScriptPromiseResolver>> m_resolvers;
 };
 
 } // namespace blink
 
 #endif // Worklet_h