Worklet: Lazily create PaintWorkletGlobalScopes

third_party/WebKit/Source/modules/csspaint/PaintWorkletPendingGeneratorRegistry.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 PaintWorkletPendingGeneratorRegistry_h
+#define PaintWorkletPendingGeneratorRegistry_h
+
+#include "modules/csspaint/CSSPaintImageGeneratorImpl.h"
+#include "platform/heap/Heap.h"
+#include "platform/heap/HeapAllocator.h"
+
+namespace blink {
+
+class CSSPaintDefinition;
+
+// Keeps pending CSSPaintImageGeneratorImpls until corresponding
+// CSSPaintDefinitions are registered.
+class PaintWorkletPendingGeneratorRegistry
+    : public GarbageCollected<PaintWorkletPendingGeneratorRegistry> {
+  WTF_MAKE_NONCOPYABLE(PaintWorkletPendingGeneratorRegistry);
+
+ public:
+  PaintWorkletPendingGeneratorRegistry() = default;
+
+  void SetDefinition(const String& name, CSSPaintDefinition*);
+  void AddPendingGenerator(const String& name, CSSPaintImageGeneratorImpl*);
+
+  DECLARE_TRACE();
+
+ private:
+  // The map of CSSPaintImageGeneratorImpl which are waiting for a
+  // CSSPaintDefinition to be registered. Owners of this registry is expected to
+  // outlive the generators hence are held onto with a WeakMember.
+  using GeneratorHashSet = HeapHashSet<WeakMember<CSSPaintImageGeneratorImpl>>;
+  using PendingGeneratorMap = HeapHashMap<String, Member<GeneratorHashSet>>;
+  PendingGeneratorMap pending_generators_;
+};
+
+}  // namespace blink
+
+#endif  // PaintWorkletPendingGeneratorRegistry_h