Run task queue manager work in batches

content/renderer/scheduler/task_queue_manager_unittest.cc

 // 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.
 
 #include "content/renderer/scheduler/task_queue_manager.h"
 
 #include "base/test/test_simple_task_runner.h"
 #include "base/threading/thread.h"
 #include "content/renderer/scheduler/task_queue_selector.h"
 #include "testing/gmock/include/gmock/gmock.h"
@@ skipping 462 matching lines @@
   runner->PostTask(
       FROM_HERE, base::Bind(&PostFromNestedRunloop, message_loop_.get(), runner,
                             base::Unretained(&tasks_to_post_from_nested_loop)));
   runner->PostTask(FROM_HERE, base::Bind(&TestTask, 2, &run_order));
 
   message_loop_->RunUntilIdle();
 
   EXPECT_THAT(run_order, ElementsAre(0, 2, 1));
 }
 
+TEST_F(TaskQueueManagerTest, WorkBatching) {
+  Initialize(1u);
+
+  manager_->SetWorkBatchSize(2);
+
+  std::vector<int> run_order;
+  scoped_refptr<base::SingleThreadTaskRunner> runner =
+      manager_->TaskRunnerForQueue(0);
+
+  selector_->AppendQueueToService(0);
+  selector_->AppendQueueToService(0);
+  selector_->AppendQueueToService(0);
+  selector_->AppendQueueToService(0);
+
+  runner->PostTask(FROM_HERE, base::Bind(&TestTask, 1, &run_order));
+  runner->PostTask(FROM_HERE, base::Bind(&TestTask, 2, &run_order));
+  runner->PostTask(FROM_HERE, base::Bind(&TestTask, 3, &run_order));
+  runner->PostTask(FROM_HERE, base::Bind(&TestTask, 4, &run_order));
+
+  // Running one task in the host message loop should cause two posted tasks to
+  // get executed.
+  EXPECT_EQ(test_task_runner_->GetPendingTasks().size(), 1u);
+  test_task_runner_->RunPendingTasks();
+  EXPECT_THAT(run_order, ElementsAre(1, 2));
+
+  // The second task runs the remaining two posted tasks.
+  EXPECT_EQ(test_task_runner_->GetPendingTasks().size(), 1u);
+  test_task_runner_->RunPendingTasks();
+  EXPECT_THAT(run_order, ElementsAre(1, 2, 3, 4));
+}
+
 }  // namespace
 }  // namespace content