scheduler: Add support for tracing scheduler state

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/gtest/include/gtest/gtest.h"
@@ skipping 19 matching lines @@
   }
 
   void AppendQueueToService(size_t queue_index) {
     queues_to_service_.push_back(queue_index);
   }
 
   const std::vector<const base::TaskQueue*>& work_queues() {
     return work_queues_;
   }
 
+  void AsValueInto(base::debug::TracedValue* state) const override {
+  }
+
  private:
   std::deque<size_t> queues_to_service_;
   std::vector<const base::TaskQueue*> work_queues_;
 
   DISALLOW_COPY_AND_ASSIGN(SelectorForTest);
 };
 
 class TaskQueueManagerTest : public testing::Test {
  protected:
   void Initialize(size_t num_queues) {
@@ skipping 299 matching lines @@
       FROM_HERE, base::Bind(&PostTaskToRunner, runner, &run_order));
   thread.Stop();
 
   selector_->AppendQueueToService(0);
   message_loop.RunUntilIdle();
   EXPECT_EQ(1, run_order[0]);
 }
 
 }  // namespace
 }  // namespace content