Run task queue manager work in batches

content/renderer/scheduler/task_queue_manager.h

 // Copyright 2014 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 CONTENT_RENDERER_SCHEDULER_TASK_QUEUE_MANAGER_H_
 #define CONTENT_RENDERER_SCHEDULER_TASK_QUEUE_MANAGER_H_
 
 #include "base/atomic_sequence_num.h"
 #include "base/debug/task_annotator.h"
 #include "base/macros.h"
@@ skipping 62 matching lines @@
 
   // Returns true if there no tasks in either the work or incoming task queue
   // identified by |queue_index|. Note that this function involves taking a
   // lock, so calling it has some overhead.
   bool IsQueueEmpty(size_t queue_index) const;
 
   // Set the name |queue_index| for tracing purposes. |name| must be a pointer
   // to a static string.
   void SetQueueName(size_t queue_index, const char* name);
 
+  // Set the number of tasks executed in a single invocation of the task queue
+  // manager. Increasing the batch size can reduce the overhead of yielding
+  // back to the main message loop -- at the cost of potentially delaying other
+  // tasks posted to the main loop. The batch size is 1 by default.
+  void SetWorkBatchSize(int work_batch_size);
+
  private:
   friend class internal::TaskQueue;
 
   // Called by the task queue to register a new pending task and allocate a
   // sequence number for it.
   void DidQueueTask(base::PendingTask* pending_task);
 
   // Post a task to call DoWork() on the main task runner.  Only one pending
   // DoWork is allowed from the main thread, to prevent an explosion of pending
   // DoWorks.
@@ skipping 35 matching lines @@
   base::ThreadChecker main_thread_checker_;
   scoped_refptr<base::SingleThreadTaskRunner> main_task_runner_;
   TaskQueueSelector* selector_;
 
   base::WeakPtr<TaskQueueManager> task_queue_manager_weak_ptr_;
 
   // The pending_dowork_count_ is only tracked on the main thread since that's
   // where re-entrant problems happen.
   int pending_dowork_count_;
 
+  int work_batch_size_;
+
   base::WeakPtrFactory<TaskQueueManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TaskQueueManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_SCHEDULER_TASK_QUEUE_MANAGER_H_