Pass per-frame task runners to Workers (when possible) [2nd try]

third_party/WebKit/Source/core/workers/ParentFrameTaskRunners.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 ParentFrameTaskRunners_h
+#define ParentFrameTaskRunners_h
+
+#include "core/CoreExport.h"
+#include "core/dom/TaskRunnerHelper.h"
+#include "core/frame/LocalFrameLifecycleObserver.h"
+#include "platform/heap/Handle.h"
+#include "wtf/Allocator.h"
+#include "wtf/Noncopyable.h"
+#include "wtf/PtrUtil.h"
+#include <memory>
+
+namespace blink {
+
+class LocalFrame;
+class WebTaskRunner;
+
+// Represents a set of task runners of the parent (or associated) document's
+// frame. This could be accessed from worker thread(s) and must be initialized
+// on the parent context thread (i.e. MainThread) on construction time, rather
+// than being done lazily.
+//
+// This observes LocalFrame lifecycle only for in-process worker cases (i.e.
+// only when a non-null LocalFrame is given).
+class CORE_EXPORT ParentFrameTaskRunners final : public GarbageCollectedFinalized<ParentFrameTaskRunners>, public LocalFrameLifecycleObserver {
+    USING_GARBAGE_COLLECTED_MIXIN(ParentFrameTaskRunners);
+    WTF_MAKE_NONCOPYABLE(ParentFrameTaskRunners);
+
+public:
+    // LocalFrame could be nullptr if the worker is not associated with a
+    // particular local frame.
+    explicit ParentFrameTaskRunners(LocalFrame*);
+
+    // Might return nullptr for unsupported task types.
+    WebTaskRunner* get(TaskType);
+
+    DECLARE_VIRTUAL_TRACE();
+
+private:
+    using TaskRunnerHashMap = HashMap<TaskType, WebTaskRunner*, WTF::IntHash<TaskType>, TaskTypeTraits>;
+
+    void contextDestroyed() override;
+
+    Mutex m_taskRunnersMutex;
+    TaskRunnerHashMap m_taskRunners;
+};
+
+} // namespace blink
+
+#endif // ParentFrameTaskRunners_h