cc: Simplify task and its derived classes.

cc/raster/single_thread_task_graph_runner.cc

 // 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.
 
 #include "cc/raster/single_thread_task_graph_runner.h"
 
 #include <stdint.h>
 
 #include <string>
 
@@ skipping 81 matching lines @@
       has_namespaces_with_finished_running_tasks_cv_.Wait();
 
     // There may be other namespaces that have finished running tasks, so wake
     // up another origin thread.
     has_namespaces_with_finished_running_tasks_cv_.Signal();
   }
 }
 
 void SingleThreadTaskGraphRunner::CollectCompletedTasks(
     NamespaceToken token,
-    Task::Vector* completed_tasks) {
+    DependencyTask::Vector* completed_tasks) {
   TRACE_EVENT0("cc", "SingleThreadTaskGraphRunner::CollectCompletedTasks");
 
   DCHECK(token.IsValid());
 
   {
     base::AutoLock lock(lock_);
     work_queue_.CollectCompletedTasks(token, completed_tasks);
   }
 }
 
@@ skipping 26 matching lines @@
       ready_to_run_namespaces.cbegin(), ready_to_run_namespaces.cend(),
       [](const std::pair<uint16_t, TaskGraphWorkQueue::TaskNamespace::Vector>&
              pair) { return !pair.second.empty(); });
 
   if (found == ready_to_run_namespaces.cend()) {
     return false;
   }
 
   const uint16_t category = found->first;
   auto prioritized_task = work_queue_.GetNextTaskToRun(category);
-  Task* task = prioritized_task.task;
+  DependencyTask* task = prioritized_task.task;
 
   // Call WillRun() before releasing |lock_| and running task.
   task->WillRun();
 
   {
     base::AutoUnlock unlock(lock_);
     task->RunOnWorkerThread();
   }
 
   // This will mark task as finished running.
   task->DidRun();
 
   work_queue_.CompleteTask(prioritized_task);
 
   // If namespace has finished running all tasks, wake up origin thread.
   if (work_queue_.HasFinishedRunningTasksInNamespace(
           prioritized_task.task_namespace))
     has_namespaces_with_finished_running_tasks_cv_.Signal();
 
   return true;
 }
 
 }  // namespace cc