cc: Remove ScheduleOnOriginThread() and CompleteOnOriginThread().

cc/raster/task.h

 // Copyright 2016 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 CC_RASTER_TASK_H_
 #define CC_RASTER_TASK_H_
 
 #include <stdint.h>
 
 #include <vector>
 
 #include "base/memory/ref_counted.h"
 #include "cc/base/cc_export.h"
 
 namespace cc {
 class Task;
 
-// States to manage life cycle of a task. Task gets created with NEW state and
-// concludes either in FINISHED or CANCELLED state. So possible life cycle
-// paths for task are -
-//   NEW -> SCHEDULED -> RUNNING -> FINISHED
-//   NEW -> SCHEDULED -> CANCELED
+// This class provides states to manage life cycle of a task and given below is
+// how it is used by TaskGraphWorkQueue to process life cycle of a task.
+// Task is in NEW state when it is created. When task is added to
+// |ready_to_run_tasks| then its state is changed to SCHEDULED. Task can be
+// canceled from NEW state (not yet scheduled to run) or from SCHEDULED state,
+// when new ScheduleTasks() is triggered and its state is changed to CANCELED.
+// When task is about to run it is added |running_tasks| and its state is
+// changed to RUNNING. Once task finishes running, its state is changed to
+// FINISHED. Both CANCELED and FINISHED tasks are added to |completed_tasks|.
+//                ╔═════╗
+//         +------║ NEW ║------+
+//         |      ╚═════╝      |
+//         v                   v
+//   ┌───────────┐        ╔══════════╗
+//   │ SCHEDULED │------> ║ CANCELED ║
+//   └───────────┘        ╚══════════╝
+//         |
+//         v
+//    ┌─────────┐         ╔══════════╗
+//    │ RUNNING │-------> ║ FINISHED ║
+//    └─────────┘         ╚══════════╝
 class CC_EXPORT TaskState {
  public:
   bool IsScheduled() const;
   bool IsRunning() const;
   bool IsFinished() const;
   bool IsCanceled() const;
 
   // Functions to change the state of task. These functions should be called
   // only from TaskGraphWorkQueue where the life cycle of a task is decided or
   // from tests. These functions are not thread-safe. Caller is responsible for
@@ skipping 84 matching lines @@
   void Swap(TaskGraph* other);
   void Reset();
 
   Node::Vector nodes;
   Edge::Vector edges;
 };
 
 }  // namespace cc
 
 #endif  // CC_RASTER_TASK_H_