[WIP] Worklet: Merge MainThreadWorklet and ThreadedWorklet into Worklet

third_party/WebKit/Source/core/workers/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 "core/CoreExport.h"
 #include "core/dom/ContextLifecycleObserver.h"
+#include "core/workers/WorkletGlobalScopeProxy.h"
 #include "core/workers/WorkletOptions.h"
 #include "platform/bindings/ScriptWrappable.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class LocalFrame;
 class ScriptPromiseResolver;
 
 // This is the base implementation of Worklet interface defined in the spec:
 // https://drafts.css-houdini.org/worklets/#worklet
 // Although some worklets run off the main thread, this must be created and
 // destroyed on the main thread.
 class CORE_EXPORT Worklet : public GarbageCollectedFinalized<Worklet>,
                             public ScriptWrappable,
                             public ContextLifecycleObserver {
   DEFINE_WRAPPERTYPEINFO();
   USING_GARBAGE_COLLECTED_MIXIN(Worklet);
   WTF_MAKE_NONCOPYABLE(Worklet);
 
  public:
   virtual ~Worklet() = default;
 
   // Worklet.idl
   // addModule() imports ES6 module scripts.
   virtual ScriptPromise addModule(ScriptState*,
                                   const String& module_url,
                                   const WorkletOptions&);
 
+  // ContextLifecycleObserver
+  void ContextDestroyed(ExecutionContext*) final;
+
   DECLARE_VIRTUAL_TRACE();
 
  protected:
   // The Worklet inherits the url and userAgent from the frame->document().
   explicit Worklet(LocalFrame*);
 
+  // Returns one of available global scopes.
+  WorkletGlobalScopeProxy* FindAvailableGlobalScope() const;
+
+  size_t GetNumberOfGlobalScopes() const { return proxies_.size(); }
+
  private:
-  virtual void FetchAndInvokeScript(const KURL& module_url_record,
-                                    const WorkletOptions&,
-                                    ScriptPromiseResolver*) = 0;
+  void FetchAndInvokeScript(const KURL& module_url_record,
+                            const WorkletOptions&,
+                            ScriptPromiseResolver*);
+
+  // Returns true if there are no global scopes or additional global scopes are
+  // necessary. CreateGlobalScope() will be called in that case. Each worklet
+  // can define how to pool global scopes here.
+  virtual bool NeedsToCreateGlobalScope() = 0;
+  virtual std::unique_ptr<WorkletGlobalScopeProxy> CreateGlobalScope() = 0;
+
+  // "A Worklet has a list of the worklet's WorkletGlobalScopes. Initially this
+  // list is empty; it is populated when the user agent chooses to create its
+  // WorkletGlobalScope."
+  // https://drafts.css-houdini.org/worklets/#worklet-section
+  // TODO(nhiroki): Make (Paint)WorkletGlobalScopeProxy GC-managed object to
+  // avoid that GC graphs are disjointed (https://crbug.com/719775).
+  HashSet<std::unique_ptr<WorkletGlobalScopeProxy>> proxies_;
 };
 
 }  // namespace blink
 
 #endif  // Worklet_h