Worker: Introduce per-global-scope task scheduler

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 "platform/wtf/Allocator.h"
 #include "platform/wtf/HashTraits.h"
 
 namespace blink {
 
 class Document;
 class ExecutionContext;
 class LocalFrame;
 class ScriptState;
 class WebTaskRunner;
+class WorkerOrWorkletGlobalScope;
+class WorkerThread;
 
 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.
 
   // https://html.spec.whatwg.org/multipage/webappapis.html#generic-task-sources
   //
   // This task source is used for features that react to DOM manipulations, such
   // as things that happen in a non-blocking fashion when an element is inserted
   // into the document.
@@ skipping 106 matching lines @@
   }
 };
 
 // A set of helper functions to get a WebTaskRunner for TaskType and a context
 // object. The posted tasks are guaranteed to run in a sequence if they have the
 // same TaskType and the context objects belong to the same frame.
 class CORE_EXPORT TaskRunnerHelper final {
   STATIC_ONLY(TaskRunnerHelper);
 
  public:
   static RefPtr<WebTaskRunner> Get(TaskType, LocalFrame*);

[altimin, 2017/04/18 00:46:40]

Not related to this CL, just to start discussion.

Do you think that these should be methods of LocalFrame, Document,
ExecutionContext, etc? Something like local_frame->GetTaskRunner(task_type)?

[nhiroki, 2017/04/18 05:34:38]

I don't have a strong opinion, but I'd slightly prefer the current
TaskRunnerHelper because the TaskType/TaskRunner mappings for documents and
workers are placed in one file. I'd like to hear others' opinions.

   static RefPtr<WebTaskRunner> Get(TaskType, Document*);
   static RefPtr<WebTaskRunner> Get(TaskType, ExecutionContext*);
   static RefPtr<WebTaskRunner> Get(TaskType, ScriptState*);
+  static RefPtr<WebTaskRunner> Get(TaskType, WorkerOrWorkletGlobalScope*);
+
+  // Returns a WebTaskRunner that is associated to the worker / worklet global
+  // scope that corresponds to the given WorkerThread. Note that WorkerThread is
+  // a per-global-scope object while the naming might sound differently.
+  // TODO(nhiroki): Rename WorkerThread to something that clarifies it's a
+  // per-global-scope object.
+  static RefPtr<WebTaskRunner> Get(TaskType, WorkerThread*);
 };
 
 }  // namespace blink
 
 #endif