Worker: Update comments about task runners for worker threads

Bug: 624696
Change-Id: I1a501ec3b90dc135fef41274818b94dd80557cc1
Reviewed-on: https://chromium-review.googlesource.com/972782Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544818}

third_party/WebKit/Source/core/workers/WorkerThread.h

@@ -202,7 +202,11 @@ class CORE_EXPORT WorkerThread : public WebThread::TaskObserver {
     return nullptr;
   }
 
-  // Can be called on both the main thread and the worker thread.
+  // Returns a task runner bound to the per-global-scope scheduler's task queue.
+  // You don't have to care about the lifetime of the associated global scope
+  // and underlying thread. After the global scope is destroyed, queued tasks
+  // are discarded and PostTask on the returned task runner just fails. This
+  // function can be called on both the main thread and the worker thread.
   scoped_refptr<base::SingleThreadTaskRunner> GetTaskRunner(TaskType type) {
     return global_scope_scheduler_->GetTaskRunner(type);
   }

third_party/WebKit/Source/modules/webdatabase/Database.h

@@ -184,9 +184,9 @@ class Database final : public ScriptWrappable {
   scoped_refptr<const SecurityOrigin> database_thread_security_origin_;
   Member<DatabaseContext>
       database_context_;  // Associated with m_executionContext.
-  // TaskRunnerHelper::get is not thread-safe, so we save SingleThreadTaskRunner
-  // for TaskType::DatabaseAccess for later use as the constructor runs in the
-  // main thread.
+  // ExecutionContext::GetTaskRunner() is not thread-safe, so we save
+  // SingleThreadTaskRunner for TaskType::DatabaseAccess for later use as the
+  // constructor runs in the main thread.
   scoped_refptr<base::SingleThreadTaskRunner> database_task_runner_;
 
   String name_;

third_party/WebKit/Source/platform/scheduler/child/worker_global_scope_scheduler.h

@@ -30,7 +30,7 @@ class PLATFORM_EXPORT WorkerGlobalScopeScheduler {
   // Returns a task runner that is suitable with the given task type. This can
   // be called from any thread.
   //
-  // This must be called only from TaskRunnerHelper::Get().
+  // This must be called only from WorkerThread::GetTaskRunner().
   scoped_refptr<base::SingleThreadTaskRunner> GetTaskRunner(TaskType) const;
 
   // TODO(nhiroki): Add mechanism to throttle/suspend tasks in response to the

third_party/WebKit/public/platform/WebThread.h

@@ -77,12 +77,12 @@ class BLINK_PLATFORM_EXPORT WebThread {
     virtual void DidProcessTask() = 0;
   };
 
-  // DEPRECATED: Returns a WebTaskRunner bound to the underlying scheduler's
+  // DEPRECATED: Returns a task runner bound to the underlying scheduler's
   // default task queue.
   //
   // Default scheduler task queue does not give scheduler enough freedom to
   // manage task priorities and should not be used.
-  // Use TaskRunnerHelper::Get instead (crbug.com/624696).
+  // Use ExecutionContext::GetTaskRunner instead (crbug.com/624696).
   virtual scoped_refptr<base::SingleThreadTaskRunner> GetTaskRunner() const {
     return nullptr;
   }