scheduler: Always create a real scheduler in unit tests

components/scheduler/renderer/lazy_scheduler_message_loop_delegate.h

+// Copyright 2015 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 COMPONENTS_SCHEDULER_RENDERER_LAZY_SCHEDULER_MESSAGE_LOOP_DELEGATE_H_
+#define COMPONENTS_SCHEDULER_RENDERER_LAZY_SCHEDULER_MESSAGE_LOOP_DELEGATE_H_
+
+#include "base/message_loop/message_loop.h"
+#include "components/scheduler/child/nestable_single_thread_task_runner.h"
+#include "components/scheduler/scheduler_export.h"
+
+namespace scheduler {
+
+// This class connects the scheduler to a MessageLoop, but unlike
+// SchedulerMessageLoopDelegate it allows the message loop to be created lazily
+// after the scheduler has been brought up. This is needed in testing scenarios
+// where Blink is initialized before a MessageLoop has been created.
+//
+// TODO(skyostil): Fix the relevant test suites and remove this class
+// (crbug.com/495659).
+class SCHEDULER_EXPORT LazySchedulerMessageLoopDelegate

[rmcilroy, 2015/06/02 16:53:07]

Maybe we should call this LazySchedulerMessageLoopDelegateForTests if this
should only be used in tests?

[Sami, 2015/06/02 17:26:20]

I thought about that but shied away because the include guards didn't fit into
80 chars anymore :) Done.

+    : public NestableSingleThreadTaskRunner {
+ public:
+  static scoped_refptr<LazySchedulerMessageLoopDelegate> Create();
+
+  // NestableSingleThreadTaskRunner implementation
+  bool PostDelayedTask(const tracked_objects::Location& from_here,
+                       const base::Closure& task,
+                       base::TimeDelta delay) override;
+  bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
+                                  const base::Closure& task,
+                                  base::TimeDelta delay) override;
+  bool RunsTasksOnCurrentThread() const override;
+  bool IsNested() const override;
+  void AddTaskObserver(base::MessageLoop::TaskObserver* task_observer) override;
+  void RemoveTaskObserver(
+      base::MessageLoop::TaskObserver* task_observer) override;
+
+ private:
+  LazySchedulerMessageLoopDelegate();
+  ~LazySchedulerMessageLoopDelegate() override;
+
+  bool HasMessageLoop() const;
+  base::MessageLoop* EnsureMessageLoop() const;
+
+  base::PlatformThreadId thread_id_;
+  // Task observers which have not yet been registered to a message loop. Not
+  // owned.
+  mutable base::hash_set<base::MessageLoop::TaskObserver*> pending_observers_;
+
+  DISALLOW_COPY_AND_ASSIGN(LazySchedulerMessageLoopDelegate);
+};
+
+}  // namespace scheduler
+
+#endif  // COMPONENTS_SCHEDULER_RENDERER_LAZY_SCHEDULER_MESSAGE_LOOP_DELEGATE_H_