Run task queue manager work in batches

content/renderer/scheduler/task_queue_manager.h

Index: content/renderer/scheduler/task_queue_manager.h
diff --git a/content/renderer/scheduler/task_queue_manager.h b/content/renderer/scheduler/task_queue_manager.h
index 100c6d570ca173b44587af4712cbeadcac30d860..a0a1a446b57be80efc3b7c8f20fa1c254b559c96 100644
--- a/content/renderer/scheduler/task_queue_manager.h
+++ b/content/renderer/scheduler/task_queue_manager.h
@@ -22,6 +22,10 @@ class TracedValue;
 }
 }
 
+namespace cc {
+class TestNowSource;
+}
+
 namespace content {
 namespace internal {
 class TaskQueue;
@@ -80,6 +84,14 @@ class CONTENT_EXPORT TaskQueueManager {
   // 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);
+
+  void SetTimeSourceForTesting(scoped_refptr<cc::TestNowSource> time_source);
+
  private:
   friend class internal::TaskQueue;
 
@@ -97,7 +109,9 @@ class CONTENT_EXPORT TaskQueueManager {
 
   // Reloads any empty work queues which have automatic pumping enabled.
   // Returns true if any work queue has tasks after doing this.
-  bool UpdateWorkQueues();
+  // |next_pending_delayed_task| should be the time of the next known delayed
+  // task. It is updated if any task is found which should run earlier.
+  bool UpdateWorkQueues(base::TimeTicks* next_pending_delayed_task);
 
   // Chooses the next work queue to service. Returns true if |out_queue_index|
   // indicates the queue from which the next task should be run, false to
@@ -118,6 +132,8 @@ class CONTENT_EXPORT TaskQueueManager {
                                   base::TimeDelta delay);
   internal::TaskQueue* Queue(size_t queue_index) const;
 
+  base::TimeTicks Now() const;
+
   scoped_refptr<base::debug::ConvertableToTraceFormat>
   AsValueWithSelectorResult(bool should_run, size_t selected_queue) const;
 
@@ -135,6 +151,10 @@ class CONTENT_EXPORT TaskQueueManager {
   // where re-entrant problems happen.
   int pending_dowork_count_;
 
+  int work_batch_size_;
+
+  scoped_refptr<cc::TestNowSource> time_source_;
+
   base::WeakPtrFactory<TaskQueueManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TaskQueueManager);