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

third_party/WebKit/Source/core/dom/TaskRunnerHelper.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 TaskRunnerHelper_h
 #define TaskRunnerHelper_h
 
 #include "core/CoreExport.h"
 #include "wtf/Allocator.h"
+#include "wtf/HashTraits.h"
 
 namespace blink {
 
 class Document;
 class ExecutionContext;
 class LocalFrame;
 class ScriptState;
 class WebTaskRunner;
 
-enum class TaskType {
+enum class TaskType : unsigned {
     // Speced tasks and related internal tasks should be posted to one of
     // the following task runners. These task runners may be throttled.
     DOMManipulation,
     UserInteraction,
     Networking,
     HistoryTraversal,
     Embed,
     MediaElementEvent,
     CanvasBlobSerialization,
     Microtask,
     Timer,
     RemoteEvent,
     WebSocket,
     PostedMessage,
     UnshippedPortMessage,
 
     // Other internal tasks that cannot fit any of the above task runners
     // can be posted here, but the usage is not encouraged. The task runner
     // may be throttled.
     Internal,
 
     // Tasks that must not be throttled should be posted here, but the usage
     // should be very limited.
     Unthrottled,
 };
 
+// HashTraits for TaskType.
+struct TaskTypeTraits : WTF::GenericHashTraits<TaskType> {
+    static const bool emptyValueIsZero = false;
+    static TaskType emptyValue() { return static_cast<TaskType>(-1); }
+    static void constructDeletedValue(TaskType& slot, bool) { slot = static_cast<TaskType>(-2); }
+    static bool isDeletedValue(TaskType value) { return value == static_cast<TaskType>(-2); }
+};
+
 class CORE_EXPORT TaskRunnerHelper final {
     STATIC_ONLY(TaskRunnerHelper);
 public:
     static WebTaskRunner* get(TaskType, LocalFrame*);
     static WebTaskRunner* get(TaskType, Document*);
     static WebTaskRunner* get(TaskType, ExecutionContext*);
     static WebTaskRunner* get(TaskType, ScriptState*);
 
     // TODO(haraken): Remove the following APIs.
     static WebTaskRunner* getUnthrottledTaskRunner(LocalFrame*);
     static WebTaskRunner* getTimerTaskRunner(LocalFrame*);
     static WebTaskRunner* getLoadingTaskRunner(LocalFrame*);
     static WebTaskRunner* getUnthrottledTaskRunner(Document*);
     static WebTaskRunner* getTimerTaskRunner(Document*);
     static WebTaskRunner* getLoadingTaskRunner(Document*);
     static WebTaskRunner* getUnthrottledTaskRunner(ExecutionContext*);
     static WebTaskRunner* getUnthrottledTaskRunner(ScriptState*);
 };
 
 } // namespace blink
 
 #endif