TaskScheduler [11] Support ExecutionMode::SINGLE_THREADED.

base/task_scheduler/scheduler_thread_pool_impl.h

Index: base/task_scheduler/scheduler_thread_pool_impl.h
diff --git a/base/task_scheduler/scheduler_thread_pool_impl.h b/base/task_scheduler/scheduler_thread_pool_impl.h
index b764f2716495438564c0820760ac3cab39969d67..4eb265f7b83b75a442d0992a3bc054c3196e4a94 100644
--- a/base/task_scheduler/scheduler_thread_pool_impl.h
+++ b/base/task_scheduler/scheduler_thread_pool_impl.h
@@ -8,6 +8,7 @@
 #include <stddef.h>
 
 #include <memory>
+#include <unordered_map>
 #include <vector>
 
 #include "base/base_export.h"
@@ -72,16 +73,17 @@ class BASE_EXPORT SchedulerThreadPoolImpl : public SchedulerThreadPool {
   void ReEnqueueSequence(scoped_refptr<Sequence> sequence,
                          const SequenceSortKey& sequence_sort_key) override;
   bool PostTaskWithSequence(std::unique_ptr<Task> task,
-                            scoped_refptr<Sequence> sequence) override;
+                            scoped_refptr<Sequence> sequence,
+                            SchedulerWorkerThread* worker_thread) override;
   void PostTaskWithSequenceNow(std::unique_ptr<Task> task,
-                               scoped_refptr<Sequence> sequence) override;
+                               scoped_refptr<Sequence> sequence,
+                               SchedulerWorkerThread* worker_thread) override;
 
  private:
   class SchedulerWorkerThreadDelegateImpl;
 
-  SchedulerThreadPoolImpl(
-      TaskTracker* task_tracker,
-      DelayedTaskManager* delayed_task_manager);
+  SchedulerThreadPoolImpl(TaskTracker* task_tracker,
+                          DelayedTaskManager* delayed_task_manager);
 
   bool Initialize(
       ThreadPriority thread_priority,
@@ -94,13 +96,27 @@ class BASE_EXPORT SchedulerThreadPoolImpl : public SchedulerThreadPool {
   // Adds |worker_thread| to |idle_worker_threads_stack_|.
   void AddToIdleWorkerThreadsStack(SchedulerWorkerThread* worker_thread);
 
-  // PriorityQueue from which all threads of this thread pool get work.
-  PriorityQueue shared_priority_queue_;
+  // Removes |worker_thread| from |idle_worker_threads_stack_|.
+  void RemoveFromIdleWorkerThreadsStack(SchedulerWorkerThread* worker_thread);
 
   // All worker threads owned by this thread pool. Only modified during
   // initialization of the thread pool.
   std::vector<std::unique_ptr<SchedulerWorkerThread>> worker_threads_;
 
+  // Synchronizes access to |next_worker_thread_index_|.
+  SchedulerLock next_worker_thread_index_lock_;
+
+  // Index of the worker thread that will be assigned to the next single-
+  // threaded TaskRunner returned by this pool.
+  size_t next_worker_thread_index_ = 0;
+
+  // PriorityQueue from which all threads of this thread pool get work.
+  PriorityQueue shared_priority_queue_;
+
+  // Single-threaded PriorityQueues.
+  std::unordered_map<SchedulerWorkerThread*, std::unique_ptr<PriorityQueue>>

[gab, 2016/04/25 21:00:20]

TODO about memory management (if we keep the map, see other comment below)

[fdoray, 2016/04/25 22:34:44]

Removed this map.

+      single_threaded_priority_queues_;
+
   // Synchronizes access to |idle_worker_threads_stack_| and
   // |idle_worker_threads_stack_cv_for_testing_|. Has |shared_priority_queue_|'s
   // lock as its predecessor so that a thread can be pushed to