cc: Simplify task and its derived classes.

cc/raster/dependency_task.h

+// Copyright 2016 The Chromium Authors. All rights reserved.

[reveman, 2016/04/05 19:14:05]

can you avoid this change as part of this patch and just keep the "Task" name
for now?

[prashant.n, 2016/04/06 00:28:11]

Ok. Should that be subsequent change or should revisit later in one go for Task
= DependencyTask and TaskGraphRunner = DependencyTaskRunner?

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CC_RASTER_DEPENDENCY_TASK_H_
+#define CC_RASTER_DEPENDENCY_TASK_H_
+
+#include <vector>
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "cc/base/cc_export.h"
+
+namespace cc {
+
+// A task with or without dependencies which can be run by a TaskGraphRunner. To
+// run a DependencyTask, it should be inserted into a TaskGraph, which can then
+// be scheduled on the TaskGraphRunner.
+class CC_EXPORT DependencyTask
+    : public base::RefCountedThreadSafe<DependencyTask> {
+ public:
+  typedef std::vector<scoped_refptr<DependencyTask>> Vector;
+
+  const DependencyTask::Vector& dependencies() const { return dependencies_; }
+
+  // Subclasses should implement these methods. ScheduleOnOriginThread() and
+  // CompleteOnOriginThread() must be called on origin thread and
+  // RunOnWorkerThread() may be called on any thread (origin or worker). The
+  // subclasses are responsible for locking and thread safety.
+  virtual void ScheduleOnOriginThread() = 0;
+  virtual void CompleteOnOriginThread() = 0;
+  virtual void RunOnWorkerThread() = 0;
+
+  void WillSchedule();
+  void DidSchedule();
+  bool HasBeenScheduled() const;
+
+  void WillComplete();
+  void DidComplete();
+  bool HasCompleted() const;
+
+  void WillRun();
+  void DidRun();
+  bool HasFinishedRunning() const;
+
+ protected:
+  friend class base::RefCountedThreadSafe<DependencyTask>;
+
+  // For creating task without dependencies.
+  DependencyTask();
+  // For creating task with dependencies.
+  explicit DependencyTask(DependencyTask::Vector* dependencies);
+  virtual ~DependencyTask();
+
+  bool did_schedule_;
+  bool did_complete_;
+  bool will_run_;
+  bool did_run_;
+
+  DependencyTask::Vector dependencies_;
+};
+
+}  // namespace cc
+
+#endif  // CC_RASTER_DEPENDENCY_TASK_H_