Worklet: Introduce PaintWorkletGlobalScopeProxy

third_party/WebKit/Source/modules/csspaint/PaintWorkletGlobalScopeProxy.h

+// Copyright 2017 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 PaintWorkletGlobalScopeProxy_h
+#define PaintWorkletGlobalScopeProxy_h
+
+#include "core/workers/WorkletGlobalScopeProxy.h"
+
+#include "modules/ModulesExport.h"
+#include "modules/csspaint/PaintWorkletGlobalScope.h"
+
+namespace blink {
+
+class CSSPaintDefinition;
+class LocalFrame;
+
+// A proxy for PaintWorklet to talk to PaintWorkletGlobalScope.
+class MODULES_EXPORT PaintWorkletGlobalScopeProxy
+    : public WorkletGlobalScopeProxy {
+ public:
+  static std::unique_ptr<PaintWorkletGlobalScopeProxy> Create(LocalFrame*);
+  static PaintWorkletGlobalScopeProxy* From(WorkletGlobalScopeProxy*);
+
+  virtual ~PaintWorkletGlobalScopeProxy() = default;
+
+  // Implements WorkletGlobalScopeProxy.
+  void FetchAndInvokeScript(const KURL& module_url_record,
+                            WorkletPendingTasks*) override;
+  void EvaluateScript(const ScriptSourceCode&) override;
+  void TerminateWorkletGlobalScope() override;
+
+  CSSPaintDefinition* FindDefinition(const String& name);
+  void AddPendingGenerator(const String& name, CSSPaintImageGeneratorImpl*);
+
+  PaintWorkletGlobalScope* global_scope() const { return global_scope_.Get(); }
+
+ private:
+  explicit PaintWorkletGlobalScopeProxy(LocalFrame*);
+
+  Persistent<PaintWorkletGlobalScope> global_scope_;

[haraken, 2017/05/01 08:43:47]

Are you pretty sure that this persistent handle doesn't create a reference
cycle?

  PaintWorklet => PaintWorkletGlobalScopeProxy => PaintWorkletGlobalScope => ...
=> PaintWorklet ?

[nhiroki, 2017/05/02 04:45:24]

Hmmm... I'm not 100% sure that this never cause the reference cycle.

To make sure to avoid it, I made TerminateWorkletGlobalScope() nullify the
handle. It's called during Document's ContextDestroyed(). Does this make sense?

[haraken, 2017/05/02 04:49:43]

Sounds good.

+};
+
+}  // namespace blink
+
+#endif  // PaintWorkletGlobalScopeProxy_h