Worklet: Separate Worklet into MainThreadWorklet and ThreadedWorklet

third_party/WebKit/Source/modules/csspaint/PaintWorklet.cpp

 // 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.
 
 #include "modules/csspaint/PaintWorklet.h"
 
 #include "bindings/core/v8/V8Binding.h"
 #include "core/dom/Document.h"
 #include "core/frame/LocalFrame.h"
 #include "modules/csspaint/PaintWorkletGlobalScope.h"
 
 namespace blink {
 
 // static
 PaintWorklet* PaintWorklet::Create(LocalFrame* frame) {
   return new PaintWorklet(frame);
 }
 
 PaintWorklet::PaintWorklet(LocalFrame* frame)
-    : Worklet(frame),
+    : MainThreadWorklet(frame),
       paint_worklet_global_scope_(PaintWorkletGlobalScope::Create(
           frame,
           frame->GetDocument()->Url(),
           frame->GetDocument()->UserAgent(),
           frame->GetDocument()->GetSecurityOrigin(),
           ToIsolate(frame->GetDocument()))) {}
 
 PaintWorklet::~PaintWorklet() {}
 
 PaintWorkletGlobalScope* PaintWorklet::GetWorkletGlobalScopeProxy() const {
   return paint_worklet_global_scope_.Get();
 }
 
 CSSPaintDefinition* PaintWorklet::FindDefinition(const String& name) {
   return paint_worklet_global_scope_->FindDefinition(name);
 }
 
 void PaintWorklet::AddPendingGenerator(const String& name,
                                        CSSPaintImageGeneratorImpl* generator) {
   return paint_worklet_global_scope_->AddPendingGenerator(name, generator);
 }
 
 DEFINE_TRACE(PaintWorklet) {
   visitor->Trace(paint_worklet_global_scope_);
-  Worklet::Trace(visitor);
+  MainThreadWorklet::Trace(visitor);
 }
 
 }  // namespace blink